(NEXSTAR) — As stories about airplane mishaps and disasters across U.S. skies continue, many air travelers may be more interested in the conditions of planes than ever before. And while age does not dictate an aircraft’s safety, you might be surprised to know just how long planes can stick around in service.

Recently, consumer finance outlet FinanceBuzz analyzed data from the civil aviation database Planespotters.net to determine which airlines currently have the oldest and newest planes. In addition to Planespotters data, we cross-referenced fleet age information from air traffic tracker/database Flightradar24.

Using this data, FinanceBuzz found that United Airlines has the oldest planes on average, with the average age of its fleet being 19.4 years. Though United has many brand new planes, Planespotters data showed 49% of the airline’s fleet is 20 years old or older. Meanwhile, Flightradar24 shows that of United’s 1,440 aircraft, its oldest planes are four Boeing 767s, which boast 33 years each.

Here’s how several other airlines fared, per Planespotters’ data:

Interestingly, several “budget” airlines were found to have the newest planes. This includes airlines like Spirit and Frontier, which boast average fleet ages of 6 years and 4.7 years, respectively.

The airline with the lowest average plane age is the Utah-based budget airline Breeze Airways, with an average plane age of 2.1 years. Seeing as how Breeze Airways is a newer operation (began business in May 2021), this isn’t all that unusual. Flightradar24 data shows that of Breeze Airways’ 39 aircraft, its oldest plane is an 18 year-old Embraer E190 jet, in addition to several of the same type that are 17 years old.

With all this information, you might be wondering how much age of a plane actually matters. And it does — but there are also many other factors that determine an aircraft’s longterm viability.

Back in 2020, Flightradar24 published an article titled “Aircraft age explained,” which helped illuminate why years might not be the best gauge of determining aircraft wear and tear. Because while a 30 year-old plane might be 30 years old, if it’s flown fewer total hours and pressurization cycles than a 5 year-old plane, the 30 year-old veteran might actually be in better shape.

Aviation news outlet Simple Flying explains that a pressurization cycle occurs when an aircraft takes off and its cabin is pressurized to allow everyone on board to be able to breathe normally at a high altitude. But Simple Flying says the process is harsh on a plane’s metal frame, causing what’s called “metal fatigue.”

With this in mind, aircraft manufacturers set a maximum pressurization cycle number, which dictates how many cycles a plane can go through and still be safe and/or repairable. Flightradar24 reports Boeing previously said its 747 aircraft are able to weather 35,000 pressurization cycles.

All in all, most contemporary commercial aircraft are designed to last between 25 and 35 years, according to Simple Flying. That equals about 30,000 pressurization cycles.