The world’s largest airline has extended its grounding of the Boeing 737 Max aircraft from early June until mid-August, resulting in the cancellation of 115 flights a day.

American Airlines announced on Monday morning (Australian time) it will be extending flight cancellations through to August 19 because of ongoing problems with the troubled Max jet.

The airline, which flies 24 of the Max craft, said the expanded cancellations represent 1.5 per cent of American’s daily flights this season.

In a letter to staff and customers, Chief Executive Doug Parker and President Robert Isom said its cancellations of about 90 daily flights will help the airline plan for the summer travel period, which is their busiest travel season of the year.

While they are “highly confident” the aircraft will be recertified prior to August 19, airline executives said they want to ensure reliability “for the peak travel season and provide confidence to our customers and team members when it comes to their travel plans”.

Once the aircraft is recertified, which the executives said they expect will happen soon, American plans to initially bring its Max aircraft back online as spares to supplement its operation as needed during the summer.

On Friday, Southwest Airlines removed the Max jet from its schedule until August 5 and United Airlines cancelled Max flights until June 5.

The US grounded Boeing’s 737 Max plane in mid-March after two deadly plane crashes.

A preliminary report revealed the Ethiopian Airlines plane that crashed last month nosedived several times before hitting the ground.

Boeing has been developing a software upgrade for an anti-stall system under scrutiny in both crashes.

It has slowed production and stopped deliveries as it works on a software fix.

The plane-maker aims to finish fixing the planes in late April, and changes would have to be submitted to the Federal Aviation Administration and foreign regulators for approval.

American has 24 Max jets and had previously planned to cancel Max flights through early June.

The airline says its reservations and sales teams will work with customers to manage their travel plans.

-with AAP