Pain in the chest and in the left arm can be indicative of a few different problems, most commonly a heart attack. This is because there are some shared nerve fibres from the heart and the left arm up to the brain, so the pain can be felt in both.

Even if this is not a heart attack, it could be something else coronary related, and therefore has a high chance of causing incapacitation very quickly. Of course, anything such as this should be told immediately to the other crew member, and a landing should be made as soon as possible to seek proper medical attention. You would not want to hide this pain, as it is much better to know about a pilot incapacitation ahead of time, to prepare and get medical help.

Other symptoms of heart attack are:

• Chest pain or discomfort. Most heart attacks involve discomfort in the centre or left side of the chest that lasts for more than a few minutes or that goes away and comes back. The discomfort can feel like uncomfortable pressure, squeezing, fullness, or pain.
• Feeling weak, light-headed, or faint. You may also break out into a cold sweat.
• Pain or discomfort in the jaw, neck, or back.
• Shortness of breath. This often comes along with chest discomfort, but shortness of breath also can happen before chest discomfort.