Take note of any passengers who bypass security measures before boarding the plane. If you notice an individual or pair of people entering the flight through some other entrance, or even through an exit, those might be air marshals. Since air marshals are armed, they are not subject to the same security checks as the other passengers.
See if there are any passengers already comfortably seated on board if you are an early boarder. Typically, airlines extend the offer to those traveling with young children or those who require extra assistance onto the plane. Air marshals might be seated even before these priority passengers since they have bypassed long security lines. They'll likely be seated in the aisle seats, as well.
Look for passengers with a clean shaven face, short hair, and business-like clothing such as a suit or tie. While several passengers could fit this description, these identifiers will help you narrow down the list of potential air marshals. These appearance standards are set by the Federal Air Marshals service, also preventing them from wearing jeans and unkempt hair. Female air marshals are held to the same standards. They might be spotted in business-like attire with their hair either cut short or pulled back and away from the face.
