Waited More Than 20 Minutes For Your Bag? You Could Get Free Miles

If you check a bag on your next flight, it may be worth keeping an eye on the clock at baggage claim. On two U.S. airlines, waiting for more than 20 minutes can come with a small consolation prize.

Alaska Airlines , Hawaiian Airlines , and Delta Air Lines both have policies promising to get checked bags to baggage claim within 20 minutes on eligible flights. When they don't, Alaska and Hawaiian passengers can receive 2,500 Atmos Rewards points or a $25 discount toward a future flight, while Delta passengers can claim 2,500 SkyMiles.

It's a potentially valuable perk for anyone who regularly checks luggage, but it's also one that's easy to miss. None of the three airlines automatically sends you a consolation prize for your extra time at baggage claim—you have to ask for it.

Here's how the guarantees work and, more importantly, how to actually collect.

Alaska Airlines and Hawaiian Airlines: 2,500 Atmos Rewards or $25 off a future flight

Alaska Airlines was an early adopter of the 20-minute baggage guarantee , introducing the policy in 2010, promising that eligible checked bags will arrive at baggage claim within 20 minutes of a flight reaching the gate. Now, as Alaska and Hawaiian Airlines continue integrating their operations , the guarantee covers eligible flights on both carriers .

If a bag misses the 20-minute window, travelers can choose between 2,500 Atmos Rewards points or a $25 discount code toward a future flight.

The important detail is when those 20 minutes begin. Alaska and Hawaiian bases the guarantee on the time the aircraft arrives at the gate—not when the carousel starts moving or when you make it from the plane to baggage claim.

That distinction can matter at a large airport, where a long walk or train ride between the gate and baggage claim might eat up a significant portion of the 20-minute window. Rather than trying to remember when you landed, check the flight's official gate-arrival time in the airlines joint app or start a stopwatch when you see the first passengers disembarking.

If the 20-minute mark comes and goes without your bag, don't leave the airport. The two airlines requires travelers to see one of its customer service agents to receive the guarantee. Keep your baggage claim ticket with you, and find an agent to report that the bag missed the promised window. Generally speaking, they're pretty good about giving you the little reward—especially at airports, like Denver, where it's physically impossible for them to route the bags to the belt on time.

The guarantee comes with some exclusions. Oversized items and animals flying in baggage claim aren't covered, for example.

Delta: 2,500 SkyMiles

Delta Air Lines has a similar deal—on eligible domestic flights, Delta promises that checked bags will reach the baggage carousel within 20 minutes. If yours doesn't, you can claim 2,500 bonus SkyMiles.

Unlike Alaska and Hawaiian, there's no airport agent required. Delta passengers submit their claim online through the airline's online form .

The program applies to domestic flights (which includes all 50 states, Washington, D.C., and Puerto Rico) that are marketed and operated by Delta or Delta Connection. If you have a connecting itinerary, the final flight needs to be marketed and operated by Delta or Delta Connection to qualify.

There are also baggage restrictions. Oversized and overweight bags and certain special items aren't eligible for the guarantee, so waiting 25 minutes for a set of golf clubs or another item routed to an oversize baggage area isn't necessarily going to earn you 2,500 miles.

Travelers also need to be SkyMiles members in good standing and have their SkyMiles number attached to the reservation to receive the bonus. The request also must be submitted online within two hours of the flight landing to earn the miles.

This article was originally published on Forbes.com