The collaboration, called Blue Sky, will see the two airlines offer flights on each other’s websites, let customers comingle their frequent-flyer points, and allow United to return to New York’s JFK airport 10 years after it gave up its slots there.

What the heck is going on—and how does it impact passengers? Here’s what you need to know.

Are JetBlue and United Airlines merging?

No. JetBlue and United will remain separate companies, but are becoming much more closely aligned. JetBlue had hoped to purchase Spirit Airlines for $3.8 billion, but was blocked last year by a federal judge, saying it would harm competition. By striking a partnership, neither United nor JetBlue needs to seek the same degree of regulatory approval that they would for a formal merger.

Will this agreement change how I book flights on JetBlue and/or United?

You’ll still be able to book JetBlue flights through JetBlue and United through United, but you’ll also be able to book flights on United routes on JetBlue’s website and app and vice versa. Basically, you’ll have expanded options on both carriers’ websites and apps (much as you do on third-party sites like Google Flights and Expedia).

This partnership is not a code-sharing agreement, however. Each airline will publish and market flights independently under its own brand and flight numbers. Additionally, the two carriers will not coordinate their schedules or share revenue.

What’s the impact on JetBlue’s and United’s frequent-flyer programs?

You’re going to have a lot more options on where you can go. United’s MileagePlus customers will be able to earn and use miles on most JetBlue flights (and JetBlue TrueBlue members can use their points on United flights). That will give United frequent flyers more access from the Northeast to the Caribbean—and JetBlue members will have a slew of international destinations made available to them.

Your perks will remain the same on both airlines. For instance, if you’re a Mosaic 2 member in JetBlue’s frequent-flyer program, you’ll board with group one on United flights (and get priority check-in, same-day changes, and other benefits). Premier Gold members with United will board with Group B on United flights. (See here for a full list of reciprocal benefits.)

Some of the details about how the frequent flyer programs will coexist have yet to be clarified, but JetBlue says “members of each airline’s loyalty program will find similar benefits over time—as well as reciprocal revenue-based miles and points accrual and reciprocal miles and points redemption—when they use and earn miles or points on the partner airline.”

When will United return to JFK?

United flights are expected to return to JFK International Airport as early as 2027. The carrier left the airport in 2015, saying it was losing money because it did not have a big enough presence to compete with other airlines. United’s CEO (who joined after that decision was made) has said that was a mistake and has been looking for a way back into JFK for several years.

How is United returning to JFK?

It’s basically a schoolyard trade. JetBlue is providing United flights access to its slots at JFK’s Terminal 6 for up to seven daily round-trip flights (destinations are TBD). United, in return, will offer JetBlue eight flights out of Newark, using its slots.

When does this agreement between JetBlue and United go into effect?

Some of the changes this partnership will create are subject to regulatory review, but JetBlue says it expects many to begin as early as this fall—though it didn’t specify which, exactly. Others, like United’s return to JFK, are still a couple of years away.