Hurricane Simon closed Puerto Vallarta to arrivals. American's free-change deadline is today

Hurricane Simon has shut Puerto Vallarta's airport to incoming flights. If you are booked to fly there, or home from there, in the next few days, your trip is probably about to change.

The good news: several big US airlines are letting you move your flight for free. The bad news: the deadlines are short, and one of them is today.

What is happening in Puerto Vallarta

Puerto Vallarta's airport says arrivals are suspended from 5 p.m. on Saturday, October 10, until 8 a.m. on Monday, October 12, local time. The airport says it made the call on the advice of the authorities. It had already warned that some airlines canceled flights on October 10 and 11.

The storm is serious. In its 6 a.m. Central time advisory on Sunday, October 11 (8 a.m. ET), the National Hurricane Center called Simon a Category 4 hurricane with winds near 150 mph. It was about 60 miles west of Manzanillo, moving north-northwest. The center expects it to be near or just inland over west-central Mexico on Sunday, and very close to the coast on Monday.

A hurricane warning covers the coast from Punta San Telmo to El Roblito. The center warns of 10 to 20 inches of rain in parts of southwestern Mexico, with up to 30 inches in spots in Michoacán, Colima and Jalisco. It says that rain could cause deadly floods and mudslides.

How to change your flight for free

Each airline has its own rules. Here is what each one says on its own website.

American Airlines. American's waiver covers Puerto Vallarta. You qualify if you bought your ticket by October 8 and were set to fly October 9 to 11. It covers every fare, even Basic Economy. You can move to a flight from October 9 to 14 without a change fee, as long as you keep the same cities and cabin. The catch: you must make the change by October 11. That's today.

Delta. Delta's waiver covers Puerto Vallarta and Guadalajara for travel on October 10 and 11. Your ticket must have been issued by October 9. Rebook by October 14, and fly by October 14, in the same cabin, and Delta waives the fare difference. You can also cancel and take an eCredit.

Alaska Airlines. Alaska's waiver covers Puerto Vallarta, Mazatlán and Manzanillo. It applies to tickets bought by October 8 for travel from October 8 to 11. You can change with no fee and no fare difference for new travel through October 14 in the same cabin. Or you can cancel and keep the money as a credit. Make the change before your original flight leaves. It only covers tickets issued by Alaska.

Southwest. Southwest's advisory covers Puerto Vallarta on Sunday, October 11. You can rebook, or fly standby, within 14 days of your original date between the same cities, without paying more for the fare.

We could not confirm United's terms on its own website before publishing. If you are flying United, check your trip on united.com or in the United app.

Our take: move first, ask later

Hurricane waivers are generous, but they are tight. They have cutoff dates for when you bought your ticket, when you were supposed to fly and when you must rebook. Miss one, and you are back to normal fare rules.

So if you are booked into or out of Puerto Vallarta this week, don't wait for the airline to cancel. Look at your trip now. If the waiver gives you a free change, take the option that keeps you safe and still works for your plans.

Also think about where you bought your ticket. If you booked through a travel agency or another airline, you may need to go through them instead. Alaska says this outright.

If your flight is canceled

A waiver is not the same as a refund. If the airline cancels your flight and you decide not to travel, US rules say you are owed your money back, not just a credit. Southwest spells this out in its advisory. It says you may be eligible for a refund of the unused ticket and any extras, like an Extra Legroom seat, if it cancels or significantly delays your flight.

What airlines owe you while you wait is a different matter. Weather is not the airline's fault, so don't count on a free hotel. Our explainer on the new DOT delay rules walks through what airlines do and don't have to cover.