Pope Francis skipped the stairs in boarding the papal plane for a two-day trip to Malta on Saturday, instead using a boarding lift for reduced mobility passengers.

The 85-year-old departed from Rome's Fiumicino Airport at 8:40 local time (0640 GMT) en route to Malta, where he will meet Prime Minister Robert Abela and dignitaries in the morning before conducting a prayer meeting at a national shrine.

Although Francis usually takes the stairs, this time he boarded with the help of a Thunderlift, which lifts passengers vertically to the height of the plane's door.

Last month, the pontiff cancelled a trip to Florence because of acute knee pain.

Pope Francis usually takes the stairs, but this time he boarded with the help of a Thunderlift, which lifts passengers up to the height of the plane's door
Pope Francis usually takes the stairs, but this time he boarded with the help of a Thunderlift, which lifts passengers up to the height of the plane's door AFP / Tiziana FABI

Francis suffers from sciatica -- which he has dubbed "a troublesome guest" -- a chronic nerve condition that causes back, hip and leg pain and has occasionally forced him to cancel official events.

In January, knee pain prevented him from personally greeting the faithful following his weekly general audience.

The condition, he said, was temporary and joked: "I hear it happens to old people, I don't know why it happens to me".

Francis underwent surgery for an inflamed large colon last year.