When it comes to business travel, expenses can add up fast—especially when you’re flying first or business class. One handy tip many savvy frequent flyers use to cut costs is upgrading flight plans at the last minute. Switching from standard to business travel at the gate can allow you to enjoy the same amenities as those who selected first class in advance, only at a fraction of the cost.

Offering cheaper upgrades at the gate makes sense for airlines because they often have open seats they couldn’t fill, so they would rather make a little bit of money upgrading someone than making no money on the seat at all. Of course, there’s no guarantee you’re always going to land a deal on a higher class seat, but if you’re willing to take the risk, the savings can be quite significant.

Some airlines even make it possible for you to upgrade without even speaking to someone at the gate. For example, when Air Canada has an opening in its business class or premium economy seats, you may receive an upgrade option when you check in on your mobile phone or on one of the self-service check-in kiosks.

The bottom line is that it never hurts to ask. You may be surprised by how easy and cheap it is to get a seat upgrade on flights that are under-booked. Airlines want to keep their customers happy, and providing a cheap (or even free) upgrade is a great way to improve public relations. Next time you’re dreading being stuck in that middle seat in the back of the plane, look into your options. You may find that luxury seating is more accessible than you thought.