Maintenance costs compound the problem. As reported earlier this week, data compiled with Aviation Week Intelligence Network’s MRO Prospector tool showed that three of every four of the GE CF34-3 engines will need to be overhauled within the next three years at a total cost of more than $1 billion, if those aircraft remain in service. But Prospector also shows that nearly every Rolls-Royce AE 3007 will need to be overhauled over the same time period, some of them more than once, at a projected cost exceeding $1.4 billion for all the engines’ operators.

The AE 3007 powers Embraer’s 37-seat ERJ-135, 44-seat ERJ-140 and 50-seat ERJ-145. It also is used for the Cessna Citation X business jet.

If SkyWest subsidiary ExpressJet, the largest operator of the ERJ, were to retain its entire fleet of these aircraft, it would need to overhaul all of the engines within the next three years at a projected cost topping $470 million. U.S.-based SkyWest says ExpressJet engine overhaul expenses are reimbursed as incurred under the regional airline’s contracts to operate the jets for Delta Air Lines and United Airlines.