Airlines are rarely required to give you a hotel voucher when flights are delayed or canceled. Here's when you can get one.

If your flight is canceled or delayed for more than four hours between 10 p.m. and 6 p.m. at a Delta contracted facility, the airline will provide you with a hotel voucher free of charge "if overnight accommodations are available," according to the airline's contract of carriage.

Delta will also provide free public ground transportation to the hotel if the hotel does not offer a shuttle service. 

If overnight accommodations are not available, Delta will provide the passenger with a "voucher that may be applied to future travel on Delta equal in value to the contracted hotel rate, up to $100." 

In the case of an overbooked flight, Delta will provide transportation to passengers who voluntarily give up their seats or who are involuntarily bumped off the flight. If this requires the passenger to stay overnight, the airline will provide hotel accommodations to the passenger at no additional cost.

The airline is not required to provide a hotel voucher if the trip disruption was caused by a "force majeure," which Delta defines as including the below events:

1. Weather conditions or acts of God.
2. Riots, civil unrest, embargoes, war, hostilities, or unsettled international conditions.
3. Strikes, work stoppages, slowdowns, lockout, or any other labor-related dispute.
4.  Government regulation, demand, directive or requirement.
5.  Shortages of labor, fuel, or facilities.
6. Any other condition beyond Delta's control or any fact not reasonably foreseen by Delta.

United Airlines will provide a hotel voucher if a passenger experiences a delay that is the fault of the airline and "is expected to exceed four hours between the hours of 10 p.m. to 6 a.m. local time," according to the airline's contract of carriage.

If a hotel room is not available, United says it will provide "reimbursement for one night's lodging in the form of an electronic travel certificate that may be applied to future travel" with the airline. 

United recommends talking to a customer service agent about overnight options to see if you're eligible for additional accommodations. 

"Although we don't provide free hotel stays if your flight is delayed or canceled for reasons outside our control, we may be able to get you discounted hotel stays and free toiletries if you can't get to your checked bags for the evening," the United Airlines website says. "If you don't need your bags for your overnight stay, they'll end up on tomorrow's flight with you."

United defines travel disruptions outside of the company's control as including:

1. Any condition beyond UA's control including, but not limited to, meteorological or geological conditions, acts of God, riots, terrorist activities, civil commotions, embargoes, wars, hostilities, disturbances, or unsettled international conditions, either actual, anticipated, threatened or reported, or any delay, demand, circumstances, or requirement due directly or indirectly to such condition.

2. Any strike, work stoppage, slowdown, lockout, or any other labor-related dispute involving or affecting UA's services.

3. Any governmental regulation, demand or requirement.

4. Any shortage of labor, fuel, or facilities of UA or others.

5. Damage to UA's Aircraft or equipment caused by another party.

6. Any emergency situation requiring immediate care or protection for a person or property.

7. Any event not reasonably foreseen, anticipated or predicted by UA.

"Whenever there's a delay or cancellation, we work with customers to get them on their way as quickly as possible. Depending on the cause, those options can include hotel and food vouchers," a spokesperson for United said in an emailed statement. 

Below is American Airline's hotel voucher policy, according to their conditions of carriage: 

"If the disruption is our fault or you're diverted to another city, and we don't board before 11:59 p.m. local time on your scheduled arrival day, we'll arrange an overnight stay or cover the cost of an approved hotel, if available. We don't guarantee reimbursement for hotel expenses if you book directly without written authorization from American Airlines.

If the delay is beyond our control, or you book your own arrangements without written authorization from American Airlines, you're responsible to pay for your hotel, meals and other expenses. An American Airlines agent may be able to help you find a hotel."

Travel disruptions defined as being out of the airline's control include the following events: 

1. Meteorological or weather conditions.
2. Civil disturbances including war, embargoes or unsettled international conditions (real or threatened).
3. Acts of terror.
4. Public health emergencies of domestic or international concern.
5. Labor disputes that involve or affect our service.
6. Government regulations or requirements.
7. Shortage of labor, fuel or facilities of American or others.
8. Any fact not reasonably foreseen or predicted by American.

JetBlue will provide meal and hotel vouchers upon the passenger's request if your "travel is disrupted due to a controllable irregularity and the passenger experiences a departure delay of six or more hours," according to the airline's contract of carriage.

The airline defines a "controllable irregularity" as a delay, cancellation, or diversion that is not caused by an event "outside of JetBlue's reasonable control."

Events considered outside of JetBlue's "reasonable control" include:

1. Weather conditions or acts of God.

2. Riots, civil unrest, protests, embargoes, pandemic declaration or public health emergency, war, hostilities, or unsettled international conditions.

3. Strikes, work stoppages, slowdowns, lockout, or any other labor-related dispute.

4. Wars, embargos, or other hostilities.

5. Government regulation, demand, directive or requirement.

6. Shortages of labor, fuel, or facilities.

7. Any other condition or cause beyond Carrier's control or any fact not reasonably foreseen by Carrier.