American Airlines doesn't allow its own employees to use their non-rev travel benefits on flights from London's Heathrow Airport because of an artificial passenger capacity cap that has been imposed on airlines.

Airlines were told to stop selling new tickets for the rest of the summer because the airport doesn't have enough staff to deal with predicted passenger numbers.

Frequent delays and mountains of lost luggage have been caused by long security screening lines and screening capacity concerns, according to an internal memo.

It is possible for airlines to comply with the new policy by suspending staff travel benefits that are so generous that the passenger is not generating any revenue.

One of the most coveted benefits of working in the airline industry is concessionary flight tickets.

Flight attendants commute from London to work on flights in the US, so the measure could leave some employees stranded in Europe.

If restrictions were not put in place, airlines would sell tickets for 104,000 passengers per day.

Most carriers aren't likely to stop selling tickets in order to meet the capacity cap. British Airways has already canceled hundreds of flights and will be able to operate the rest of their schedule.

The airport wants the airlines to reduce capacity now because they haven't done so yet.

During the week of July 18 to July 25 American Airlines will only allow non-rev travel. Employees were warned that the embargo could be extended.

Mateusz Maszczynski

As an international flight attendant, Maszczynski worked at the most prominent airline in the Middle East and has been flying for a well-known European airline. He is an expert in passenger experience and human-centered stories. Some of the biggest names in journalism rely on Matt's industry insights, analysis and news coverage often.