The summer travel season is turning out to be a nightmare for some passengers.

During key holiday weekends like July 4 and June 16, airlines canceled thousands of flights and wreaked havoc at airports.

One traveler, Sheila Gray, had a particularly tough time on Saturday when her American Airlines flight from Charlotte to Boston suffered a five-hour maintenance delay, followed by pilot shutdowns. This means that the crew could not fly legally because they had reached the maximum number of hours they could work that day or would land at their destination after their maximum duty time.

Passengers were already on board when the crew went off duty, forcing customers to disembark.

The incident left travelers distraught and angry, Gray told Insider, saying some customers were yelling at gate agents.

In the event of disembarkation after having already been boarded, passengers have rights in certain cases, in particular if they have been involuntarily asked to leave the aircraft. Here’s what you need to know and do.

Check your flight status

Just because you were on the plane before you were asked to disembark doesn’t necessarily mean you get additional compensation. Once you get off the plane, you need to check your flight status.

If the flight is still delayed, the US Department of Transportation does not require the airlines to provide any compensation, so you will have to wait for the flight to depart or be cancelled. While you wait, ask the airline for a meal or hotel voucher as some provide it during long delays.

If the flight is cancelled, the POINT obliges the airline to provide a refund, regardless of the reason for the cancellation. However, you can instead request to be re-booked on a later flight, or choose to find your own transportation to your final destination. Airlines are not required to give you a hotel or reimburse you for travel expenses outside of flight reimbursement, per DOT.

Involuntary disembarkation

In some cases, not all passengers will be disembarked after boarding, but only a select few. This is called “cumping” or “involuntary denied boarding”, according to the DOT, and occurs when airlines oversell a flight, meaning there are more passengers than seats.

More often than not, airlines ask for volunteers to take a different flight, such as Delta Air Lines offering $10,000 to each passenger who gave up their seat on a June 27 flight from Grand Rapids, Michigan.

However, sometimes carriers do not find enough volunteers and unintentionally jostle people, which mostly happens before boarding the plane. In this case, airlines must provide compensation, although there are a few exceptions, according to the DOT:

• Change of aircraft to a smaller aircraft for operational or safety reasons
• The plane contains less than 30 people
• Weight and Balance Issues for Aircraft with 60 Seats or Less
• The flight is departing from a foreign country and heading to the United States

If none of these conditions apply and you have a confirmed ticket, checked in on time, were at the gate on time and the airline was unable to get you at your final destination within one hour of your original arrival time, you are entitled to a denied boarding allowance (DBC), according to the DOT.

DBC is based on the value of your ticket, the length of your delay resulting from involuntary denied boarding and whether your flight was domestic or international.

For domestic flights that arrive one to two hours later than scheduled, passengers receive 200% of their one-way fare, which can be capped at $775. Anything over two hours is 400%, which can be capped at $1,550.

For international flights that arrive one to four hours later than scheduled, passengers receive 200% of their one-way fare, and anything over four hours is 400%. Caps still apply, at the discretion of the airline.

Passengers who booked a higher fare class, such as business, but were downgraded to a cheaper cabin should be refunded the difference in price.

Airlines cannot remove you from a flight you have already boarded if you checked in before the last check-in time and your boarding pass was scanned at the gate, per DOT.

However, you can still be deported for safety, security or health reasons. Or, if you were a disruptive passenger. If you were removed for a reason beyond your control, such as unruly behavior, the airline is required to compensate you.

Long delay on the tarmac

Tarmac delays occur when passengers on an arriving or departing aircraft do not have the opportunity to get off the aircraft, according to DOT. In the United States, airlines are required to allow passengers to disembark a plane before three hours have passed for domestic flights and four hours for international flights.

The only exception is if the reason is related to safety, security or air traffic control.

If you sit on the plane for more than three or four hours, you can file a complaint against the airline, according to CN Traveler.

For tarmac delays longer than two hours, airlines must provide passengers with water and snacks, per DOT.

Passengers are allowed to get off the plane during tarmac delays if the airline deems it safe. However, travelers can do so at their own risk as the carrier is not required to let them reboard the plane or wait for them once the flight is ready to take off.

Also, their checked baggage should not be removed before departure, according to the DOT.