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Barriers to Effective Communication: Implications for the Cockpit

By Robert Baron
Reprinted with permission from The Aviation Consulting Group


The communication process encompasses every single part of our daily being. The use of both verbal and non-verbal communication is the very basis of how we converse, both on a personal and on a business level. This paper introduces the concepts of the communication process and then uses the aviation domain to exemplify how barriers to effective communication may manifest themselves. Two specific areas in aviation are discussed; barriers to effective communication between pilots, and, barriers to communication between pilots and air traffic controllers (ATC). The combination of case examples, empirical research, and studies of literature, is combined to give the reader a true picture of the effects of deficient communications processes in the aviation domain.

Introduction to the Problem

Effective communication is an important process in everyday life. People must be able to communicate effectively with each other on both a personal as well as business level. Breakdowns in the communication processes can lead to benign misunderstandings, or worse, a major disaster.

Nowhere else is the communication process more important than in the cockpit of an aircraft. As history has repeatedly shown, a breakdown in the communication process often leads to less than desirable events that can be illustrated as follows:

In 1977, at Tenerife in the Canary Islands, heavy accents and improper terminology among a Dutch KLM crew, an American Pan Am crew and a Spanish air traffic controller led to the worst aviation disaster in history, in which 583 passengers perished.

In 1980, another Spanish air traffic controller at Tenerife gave a holding pattern clearance to a Dan Air flight by saying "turn to the left" when he should have said "turns to the left" - resulting in the aircraft making a single left turn rather than making circles using left turns. The jet hit a mountain killing 146 people.

In 1990, Colombian Avianca pilots in a holding pattern over Kennedy Airport told controllers that their 707 was low on fuel. The crew should have stated they had a "fuel emergency," which would have given them immediate clearance to land. Instead, the crew declared a "minimum fuel" condition and the plane ran out of fuel, crashing and killing 72 people.

In 1993, Chinese pilots flying a U.S.-made MD-80 were attempting to land in northwest China. The pilots were baffled by an audio alarm from the plane's ground proximity warning system. A cockpit recorder picked up the pilot's last words: "What does 'pull up' mean?"

In 1995, an American Airlines jet crashed into a mountain in Colombia after the captain instructed the autopilot to steer towards the wrong beacon. A controller later stated that he suspected from the pilot's communications that the jet was in trouble, but that the controller's English was not sufficient for him to understand and articulate the problem.

On November 13, 1996, a Saudi Arabian airliner and a Kazakhstan plane collided in mid-air near New Delhi, India. While an investigation is still pending, early indications are that the Kazak pilot may not have been sufficiently fluent in English and was consequently unable to understand an Indian controller giving instructions in English.

( Aviation Today: Special Reports, 2004)

All of the above examples are the result of "language barriers." But, barriers to effective communication can come in other forms as well, including noise, vibration, radio clutter, distractions, and even cultural differences between crewmembers. This list is not all-inclusive, but does depict some of the more common problems in today's cockpits.

What is Effective Communication?

In order to facilitate effective communication, one must understand how the process works. In its most basic model, two-way communication involves a sender, a message and a receiver. In some communications processes, communication might be one-way, but for the purpose of this paper, only the two-way process is identified. The following illustration shows the two-way communication process.

Sender (Encodes) >Message> Receiver (Decodes)> Receiver Becomes Sender and Encodes> Message> Receiver (Decodes) - (Zastrow, 2001)

When effective communication is at work, what the receiver decodes is what the sender sends (Zastrow, 2001). A breakdown in the communication process may occur if the intended message was not encoded or decoded properly. Comments may be taken the wrong way, a compliment may be taken as an insult, or a joke might be interpreted as a put-down. There may also be barriers in the transfer process; these barriers may include:

  • Noise, static
  • Multiple communications
  • Fatigue, stress
  • Distractions
  • Incomplete message
  • Ambiguous wording
  • Lack of credibility
  • Lack of rapport
  • Think in personal terms
  • Jargon
  • Boring

(Kirby, 1997)

Further examples of barriers to effective communication are extracted from the flight instruction domain. (2004) suggests that misunderstandings stem primarily from four barriers to effective communication:

1. Lack of common experience - the transfer of words from the instructor to the student are often misunderstood or not interpreted correctly. A communicator's words cannot communicate the desired meaning to another person unless the listener or reader has had some experience with the objects or concepts to which these words refer. Many words in the English language mean different things to different people.

2. Confusion between the symbol and the symbolized object - Results when a word is confused with what it is meant to represent.

3. Overuse of abstractions - over dependence of words that are of a general nature rather than specific.

4. Interference - Includes physiological, environmental, and psychological interference.

With this basic understanding of the communication process and its limitations, let us take a look at how all of this plays into the realm of cockpits and air traffic control (ATC).

Communications Between Pilots

So big was the problem with communication in the cockpit that NASA launched an all- out study of jet transport accidents and incidents between 1968 and 1976 (Cooper, White & Lauber, 1980; Murphy, 1980) and found that pilot error was more likely to reflect failures in team communication and coordination than deficiencies in technical proficiency.

Data suggest that deficient interpersonal communication has been identified as a causal factor in approximately 70% to 80% of all accidents over the last 20 years (NASA study). Additional data from NASA's Aviation Safety Reporting System (ASRS) showed that over 70% of the first 28,000 confidential (self-disclosure) pilot reports that were received were related to communications problems (Connell, 1995).

Empirical evidence shows that specific language variables are moderately to highly correlate with individual performance, individual error rates, and individual communication ratings. Use of the first person plural (we, our, us) increases over the life of a flight crew and captains speak more in the first person plural than first officers or flight engineers (Helmreich & Sexton, n.d.). When the words (I or me) are used, there tends to be a separation of individuals leading to a degradation of the team concept.

Communications may also be hindered by subordination problems. Federal Aviation Regulation (FAR) 91.3 states, "The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft" (Code of Federal Regulations, 2004). The First Officer (F/O) must be able to act as both an assertive individual and as a subordinate in a team atmosphere. This basic dichotomy establishes the premise of a very fine balance that must be constantly maintained for proper communication to occur. Speaking up to a superior can be difficult for some people. However, not speaking up can have tragic results, as illustrated in the following cockpit voice recorder (CVR) transcript from the 1982 crash of Air Florida Flight 90 into the Potomac River in Washington, DC.


Military Time- Local

CA- Captain

F/O- First Officer

TWR- Tower

15:59:51 CA It's spooled. Real cold, real cold.

15:59:58 F/O God, look at that thing. That doesn't seem right, does it? Uh, that's not right

16:00:09 CA Yes it is, there's eighty

16:00:10 F/O Naw, I don't think that's right. Ah, maybe it is.

16:00:21 CA CAM-1 Hundred and twenty.

16:00:23 F/O  CAM-2 I don't know

16:00:31 CA Vee-one. Easy, vee-two

16:00:39 [Sound of stick shaker starts and continues until impact]

16:00:41 TWR Palm 90 contact departure control.

16:00:45 CA Forward, forward, easy. We only want five hundred.

16:00:48 CA Come on forward....forward, just barely climb.

16:00:59 CA Stalling, we're falling!

16:01:00 F/O Larry, we're going down, Larry....

16:01:01 CA I know it.

16:01:01 [Sound of impact]

(, 2004)

In this example, the First Officer notices that something is wrong with the engine instruments (highlighted in black), but the Captain disregards the F/O's concerns and continues with the takeoff. In fact, the F/O addresses the issue of something "not being right" six times, with one of those six almost an acceptance of the problem. The captain, for whatever reason, justified those "things" as being "normal" and did not use any of the conflicting information offered by the F/O.

What the F/O should have done was voice his concerns in a more assertive fashion (as the message sender, his message was not being received). Typically, if something does not look right by the pilot not flying (in this case the F/O), an "abort" callout should be made and the pilot flying (in this case the Captain) should unquestionably abort the takeoff as per the takeoff briefing. Would a more assertive F/O have prevented this catastrophe? Was the F/O's fear of job repercussions a factor in not speaking up to a superior (and highly experienced) Captain? Would the Captain have even performed an abort procedure if the F/O were more assertive? We will never know these answers. But in its purest form, there was a lack of communication.

All aircraft accidents provide us with an insight and hopefully an explanation as to what went wrong and why. Accidents are also investigated to make sure controls are established or modified to prevent that type of accident from ever happening again. The Air Florida crash was no exception. This example of deficient communicative ability has been used as a case-learning example to this very day in crew resource management (CRM) airline training programs to help crews understand their roles and communicative requirements in the cockpit.

Another example of barriers to effective communication may be found in the crew pairing process, and specifically the cultural differences between crewmembers. In this world of cultural diversity, it is not uncommon to have two pilots with a completely different cultural background flying as a crew. Verbal and nonverbal communications may be interpreted differently, and this may have implications during flight, particularly in high-workload situations.

Power Distance (PD) is the distribution of "power" among individuals and groups in a society, and how inequalities in power are dealt with in these societies (Hofstede, 1980). Societies with a low PD believe that, among other things, inequality should be minimized, all people should be interdependent, and hierarchy is an inequality of roles. Conversely, societies that believe in a high PD feel that inequality is a fact of life, hierarchy is something that exists and is accepted, and power gives privileges (Helsinki University, 2004).

In practical terms, PD reflects the fact that there is an unequal power relationship in the cockpit, and a subordinate should not question the decisions or actions of their superiors (Helmreich, Wilhelm, Klinect and Merritt, 2001). The results of a cross-cultural study, conducted by Helmreich et al. (2001), showed that in cultures with a high PD, safety might suffer from the fact that insubordinates may not have the ability to "speak up" when they should or are unwilling to make inputs regarding leaders' actions or decisions. It was found that countries such as Morocco, the Philippines, Taiwan, and Brazil had the highest PD scores, or a culture based on the acceptance of unequally distributed power. Countries such as Ireland, Denmark, Norway, and the United States scored at the extreme low end of the PD scale.

Pilot/Air Traffic Control Communications

The previous discussion covered some of the inherent problems of pilot-to-pilot communications. This segment will highlight the deficiencies in the communication process between pilots and air traffic controllers (ATC). Referring back to the beginning of this paper, one should note that out of the six accident scenarios illustrated, five of them had implications of pilot/ATC miscommunications.

The common thread among many of the examples appears to be "language barriers." Although English is the unofficial international language of aviation (CNS Outlook, 1996), the command of the English language for many foreign pilots is deficient, compounded by dialects, accents, and semantic misinterpretations. The lack of English proficiency is apparent from both the ATC, as well as the pilot side of the spectrum. This problem is not one-sided, however, because just as foreign carriers are required to be proficient in aviation English phraseology, US crews flying to other countries must also be able to understand controllers' limited, staccato, and sometimes incomprehensible English instructions.

Another area of concern in pilot/controller communication addresses "read backs" and "hear backs." Read backs are very important because they confirm that the instructions given by the controller have been understood and will be complied with by the pilot (Orlady & Orlady, 1999, p.140). The "expectancy" of further instructions often manifests itself in pilot/controller communication misunderstandings. The following example illustrates this problem:

It is not unusual for a pilot climbing out to read back a clearance reporting at 16,000 ft. when he/she was really cleared to 14,000 ft., and not have the discrepancy noted by the controller. In one example, the aircraft was cleared to an altitude of 14,000, and told to expect a later altitude of 16,000 ft. The pilot expected to hear 16,000 and reported going to 16,000 ft. Because 14,000 was the altitude assigned by the controller, this altitude was the controller's expected altitude and this was the altitude he thought he heard. Both the pilot and the controller were mistaken. (Cited in Orlady and Orlady, 1999, p.142)

Related to, but slightly different from read back, is hear back. In this case, the controller must evaluate the pilot's read back to make sure that the clearance is clearly understood and will be complied with. This may be viewed as a closed-loop system, or a system that uses redundancy to verify that what is being said is truly understood and there are no ambiguities or discrepancies in the communication process.

The process of pilot/controller communication is further complicated by environmental variables known as clipping, masking, and blocking/distortion (p.141). Masking occurs when speech is difficult to understand because of unwanted noise. For example, the cockpit of an aircraft (particularly during takeoff and climb phases) can be quite noisy. This masking of important pilot/controller instructions can lead to misunderstandings or having to request repeated instructions a number of times.

Clipping occurs when a speaker does not use a microphone properly. A pilot may inadvertently begin to speak before keying a microphone, or, unkey the microphone before finishing his or her transmission. This can lead to broken communication, clutter, and frustration for others using the frequency.

Blocking is a very common problem in ATC communications. If two pilots are trying to inadvertently transmit at the same time, the transmission will be blocked and everyone listening on the frequency will hear an ever familiar "screeching" or irritating "whistle". A "stuck" microphone can literally prevent everyone from talking or listening on the entire frequency.

Blocking may have been a contributing factor in the worst aviation disaster in history. In 1977, at Tenerife in the Canary Islands, two 747's (one operated by KLM and the other by Pan Am) collided on the runway, killing 583 passengers. In addition to factors such as improper terminology and weather conditions, the following extraction from the official accident investigation report indicates that a critical part of a takeoff clearance transmission may have been blocked:

However, in order to make their own position clear, they said, "We are still taxiing down the runway." This transmission coincided with the "Stand by for take-off ... I will call you", causing a whistling sound in the tower transmission and making its reception in the KLM cockpit not as clear as it should have been, even though it did not thereby become unintelligible. (Secretary of Aviation Report on Tenerife Crash, 1978)

A final example of pilot/controller communication comes in the form of similar sounding words and numbers. Misunderstanding of words and numbers is exacerbated by the environmental factors prevalent in the cockpit (i.e., noise, vibration, chatter, etc.). Anecdotally speaking, the author fully understands the difficulties in sorting out words and numbers, particularly in high workload and high ambient noise situations (i.e., just after takeoff). Does "five thousand" sound similar to "nine thousand?" It sure does. Do all pilots and air traffic controllers always use the proper aeronautical pronunciation of the number "nine" (it should be pronounced nine-er) to mitigate this problem? Of course not. Commonly confused words and numbers are just another part of the barriers to effective communication between pilots and controllers.


Although there are a number of examples of barriers to effective communications in this paper, it is by no means exhaustive. There are many more examples of how the process of communication works (whether good, bad, or indifferent), which can fill a 500-page book.

Aviation happens to be one of the best models for studying the communications process and its inherent flaws. This paper may have brought to light the magnitude of the communication problems in aviation; a problem for which there is no quick cure or magic potion.

Pilots and air traffic controllers must understand the limitations of communications and work toward the common goal of making the skies safer and easier to "understand!"


Aviation Today: Special Reports (2004). Report on aviation safety. Language barriers. Retrieved May 31, 2004 from

CNS Outlook (1996). Indian Air Disaster Raises Concerns About ATC Communications. Cited in Aviation Today: Special Reports.

Code of Federal Regulations (2004). Federal Aviation Regulations [electronic version].

Connell, L. (1995). Pilot and controller communications issues. In B.G. Kanki & O.V. Prinzo (Eds.), Proceedings of the Methods and Metrics of Voice Communication Workshops.

Cooper, G. E., White, M. D., Lauber, J. K. (Eds.). (1980). Resource management on the flightdeck: Proceedings of a NASA/Industry workshop (NASA CP '2120). Moffett Field, CA: NASA-Ames Research Center. (2004). Effective communication. Retrieved May 31, 2004 from

Helmreich, R. L., & Sexton, B. J. (n.d.). Analyzing cockpit communication: The links between language, performance, and workload. The University of Texas at Austin. Department of Psychology.

Helmreich, R. L., Wilhelm, J. A., Klinect, J. R., & Merritt, A. C. (2001). Culture, error, and Crew Resource Management. The University of Texas at Austin. Department of Psychology.

Hofstede, G. (1980). Culture's consequences: International differences in work-related values. Beverly Hills, CA: Sage

Kirby, J (1997). Crew Resource Management (CRM) PowerPoint presentation. A presentation of the Salt Lake City Flight Standards District Office (FSDO).

Murphy, M. (1980). Review of aircraft incidents. Cited in Cooper et al.

Orlady, H. W., & Orlady, L. M., (1999). Human factors in multi-crew flight operations. Brookfield, VT: Ashgate. (2004). Cockpit Voice Recording transcript of Air Florida Flight 90. Retrieved May 14, 2004 from

Secretary of Aviation Report on Tenerife Crash (1978). KLM, B-747, PH-BUF and Pan Am B-747 N736 collision at Tenerife Airport Spain on 27 March 1977. Retrieved from

Zastrow, C. (2001). Social work with groups: Using the class as a group leadership laboratory (5th ed.). Pacific Grove, CA: Brooks/Cole.

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