Airlines flying Boeing-737s into New Zealand have engines now subject to checks following the fatal Southwest Airlines accident.

The CFM56-7B engines are fitted to 737s which Virgin Australia and Qantas operate across the Tasman and Fiji Airways flies from Nadi.

Virgin Australia says a limited number of repairs are needed but its schedule will not be disrupted while Qantas says a small number of engines will need further inspection but none of its flights will be affected.

Following the Southwest tragedy, the United States Federal Aviation Administration and Europe's The FAA and European Aviation Safety Agency issued emergency airworthiness directives (AD) calling for inspections of fan blades on CFM engines that power Boeing 737NGs.

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In the accident a fan blade apparently snapped, hurling debris that broke a window. Passenger Jennifer Riordan was partially sucked out and died of her injuries.

Virgin Australia operates more than 80 Boeing 737-700s and Boeing 737-800s, including on Tasman routes, and said it was fulfilling all engine manufacturers' recommendations and regulatory requirements.

CFM is recommending that airlines perform ultrasonic fan-blade inspections "within the next 20 days" on frequently used engines. The engine-maker recommends inspections at different thresholds for all blades, with the most frequently used highest-time blades — those with 30,000 take-offs and landings — needing inspections immediately.

Virgin says it doesn't have engines, which have accumulated more than 30,000 cycles, but it has identified a small number of individual blades which have done so, and as a precaution these will be replaced.

''There will be no impact to customers or to the safety of our operation while these inspections occur.''

The FAA says the ultrasonic inspections of all 24 fan blade dovetail concave and convex sides are aimed at detecting cracking.

More lightly used engines need to be inspected by CFM recommends inspections "by the end of August" for fan blades with 20,000 cycles.

Qantas has about 70 Boeing 737-800s.

It says a small number of engines on its Boeing 737-800 fleet currently require further inspections.

''These inspections will be completed by our engineers within the required timeframe."

None of the Qantas engines have to be 'urgently' as they are not at the 30,000 flights stage.

Some engines need to be inspected by August 31 as they will have done between 20,000 to 29,999 flights.

Fiji Airways said its 737s were also equipped with the engines under increased scrutiny.

''But given their relatively lower life cycles none of our engines are required to undergo immediate inspection,'' a spokeswoman said.

All of its engines had been reviewed and if required would undergo inspection within the manufacturers' prescribed period.

''We do not anticipate schedule changes caused by the inspections, however, will advise guests if any changes are necessary.'

No airlines flying domestic routes in New Zealand use Boeing 737s. Air New Zealand moved to Airbus A320s which don't have the engines at the centre of the alert.