FARNBOROUGH, England, July 18 (Reuters) - Jet engine maker

CFM International said it had won U.S. and European approvals

for an upgrade that would improve durability of engines used on

Boeing 737 MAX jets.

The world's largest engine maker by units sold, jointly

owned by GE Aerospace and France's Safran, said

the "durability kit" for LEAP-1B engines would echo improvements

available for Airbus A320neo jets powered by the LEAP-1A model.

It will double "time on wing" or gaps between key repairs in

hot and harsh environments like the Middle East and India, CFM

executives told a briefing ahead of the Farnborough Airshow.

Long waiting times for repairs have been a major concern for

airlines and hobbled part of their fleets in recent years,

though disruption has been gradually easing.

The problems stem from significant fuel savings in the

latest generation of engines that were only achieved at the

expense of unexpectedly high wear and tear, lengthening waiting

times for repairs and forcing some airlines to ground aircraft.

CFM said it had now reached a "near zero" number of

LEAP-powered planes being grounded due to maintenance delays.

Rival Pratt & Whitney, which competes with CFM to power

A320neo jets, has reported steady improvement in disruption from

maintenance delays and metal contamination issues.

CFM said its new update can be added during maintenance and

will be included on the production line for new engines.