Whether before takeoff or after landing, tarmac delays can bring even the most seasoned traveler to his or her knees. Luckily, airlines are required by law to follow some guidelines, but there are a few exceptions to these rules that, if you’re not aware of them ahead of time, could morph any lengthy tarmac delay into a full-blown nightmare.
In general, the DOT prohibits any domestic tarmac delay from going beyond three hours (four hours for international flights) unless there's a legit safety or security concern or if doing so would disrupt airport operations. The former is at the discretion of the pilot and the latter of air traffic control.
During the duration of a tarmac delay, the airline must also maintain a comfortable cabin temperature and provide access to medical assistance and operable bathrooms. Plus, each passenger must be given water and a snack within two hours unless doing so violates a safety or security concern. Alas, carriers are under no obligation, regardless of the length of the delay, to offer full meals, though.
While the DOT stipulates a three-hour limit for tarmac delays, it isn't clear what your rights are if the suspension should, unfortunately, extend beyond that.
Additionally, while you can technically request to exit the plane after three hours, the airline has every right to reject your request. Plus, it is not required to let you back on and can leave without you if cleared for take off. Even worse? If you decide to depart the plane when given permission, the airline is under no obligation to offload your luggage, if or when the aircraft is given the green light for departure.
In other words: In the case of a tarmac delay, you have the right to a restroom, water and peanuts, and not much else.