* Engine spending at six U.S. airline operations far

outpaced flying since 2019

* Some newer engines need heavier, costlier repairs

* Replacement-engine leases can outlast repairs

* Aircraft delivery delays prolong maintenance on older jets

By Rajesh Kumar Singh

CHICAGO, Aug 14 (Reuters) - Airlines are getting grounded

jets back into the air. The bills left by a years-long engine

crisis are proving much harder to bring down.

Air New Zealand ( ANZFF ) offers a glimpse of how those costs

can linger. Engine problems at one point left as much as 20% of

its fleet unavailable, forcing it to lease extra aircraft and

engines to protect its schedule.

Availability has since improved sharply, but Chief Executive

Nikhil Ravishankar told Reuters it could take 12 to 18 months to

shed the extra leases and related costs, only partly offset by

supplier compensation.

The crisis was fueled by durability problems affecting some

newer engines and a Pratt & Whitney powder-metal problem that

forced accelerated inspections and removals, compounded by

shortages of labor, parts and repair capacity. Airlines leased

replacement engines and aircraft to keep flying, leaving them

with higher overhaul, parts and lease costs even as groundings

ease.

Delayed deliveries from Boeing ( BA ) and Airbus

are adding to the pressure by keeping older jets in service

longer and pushing some airlines into engine work they had

expected to avoid.

A Reuters analysis of U.S. Transportation Department data

found that across six large U.S. airline operations, reported

spending on engine labor, aircraft-engine repairs and engine

materials rose about 68% between 2019 and 2025, while hours

flown increased about 10%.

The same pattern appeared in the latest available

Transportation Department data, with reported spending in those

categories up 17% in the first quarter from a year earlier while

hours flown increased less than 2%.

Maintenance spending can vary with engine age, accumulated

cycles, fleet-management decisions and the timing of shop

visits, during which engines are removed from aircraft for

inspection or repair. The Transportation Department data do not

identify what caused the increase.

GE Aerospace, Safran and RTX did not

respond to requests for comment. Rolls-Royce declined to

comment.

RTX's Pratt & Whitney illustrates the disconnect. Groundings

tied to its geared-turbofan engines, which power many newer

single-aisle jets, fell 25% in the first half. But in the second

quarter, the mix of heavier PW1100G repair work was 14

percentage points higher than a year earlier.

Latest regulatory filings from United Airlines and

American Airlines ( AAL ) also show higher first-half

maintenance expenses driven partly by engine-overhaul work.

Parts and other materials account for about 60% of the direct

cost of a typical single-aisle engine overhaul, according to

consultancy Oliver Wyman. Newer engines deliver fuel-efficiency

gains, but overhaul bills are higher because they have fewer

developed repair options and fewer used parts available, partner

Sam Sargent said.

George Dimitroff, head of valuations at Ascend by Cirium, said

overhaul and mandatory parts-replacement costs for newer LEAP

and GTF engines, which power most Airbus A320neo- and Boeing 737

MAX-family jets, have risen about twice as much since 2019 as

for older CFM56 and V2500 engines.

Not all the maintenance growth on newer engines is tied to

technical problems; maturing fleets also require more scheduled

work.

LEASES OUTLAST GROUNDINGS

Long shop visits can force airlines to lease replacement

engines.

JetBlue Airways ( JBLU ) has said some Pratt engines can

take 200 to 300 days to complete a shop visit. The airline has

also increased the number of engines it leases.

Short-term leases for some newer LEAP and PW1100G engines

have exceeded $6,500 a day in completed transactions over the

past year, compared with around $5,000 a day in 2022-23,

according to aviation consultancy IBA.

Austin Willis, CEO of engine lessor Willis Lease Finance ( WLFC )

, told Reuters airlines needing replacement engines have

often sought leases lasting around three years, while shorter

contracts are frequently extended. That can leave airlines

paying even after their own engines return.

OLD JETS, NEW BILLS

A full overhaul of a CFM56-5B engine used on older Airbus

A320-family jets can easily cost more than $10 million, Willis

said.

Oliver Wyman and the International Air Transport Association

estimated that delayed aircraft replacements could have added

about $3.1 billion to global airline maintenance costs in 2025.

Delayed aircraft retirements are also tightening the supply

of cheaper used engine parts. Industry officials and experts say

fewer engines are being dismantled for parts, pushing up

used-parts prices and leaving airlines more dependent on new

parts from manufacturers.

PRICING TENSIONS

The squeeze has sharpened tensions between airlines and engine

makers over repair costs and pricing.

Asked at the International Air Transport Association annual

meeting in June whether engine makers had too much pricing power

and were using shortages to charge airlines more, United Chief

Executive Scott Kirby replied: "Yes and yes."

Industry executives say developing new technology costs

billions of dollars and manufacturers often discount engines

heavily upfront, expecting to recover that investment over years

through parts and maintenance.

Safran CEO Olivier Andriès last month said increases in

repair and spare-parts prices should be moderate and reflect

higher supplier costs rather than an "abusive posture."

GE Aerospace CEO Larry Culp said last month that

LEAP-related aircraft groundings had fallen to near zero. GE is

also rolling out upgraded parts designed to let the engines stay

on aircraft longer before needing major maintenance.

RTX, which said it is improving durability and expanding

repair capacity, reported Pratt's PW1100G repair output rose 43%

in the second quarter from a year earlier and turnaround times

fell 23%.

For airlines, the financial relief can take longer.

"The fact that AOGs (aircraft on ground) have come down,

that doesn't change the maintenance cost," Willis said.