Pope Francis boards his plane from a lift designed for the boarding and off boarding of reduced mobility passengers, on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

Pope Francis boards his plane from a lift designed for the boarding and off boarding of reduced mobility passengers, on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

Pope Francis (C) boards his plane from a lift designed for the boarding and off boarding of reduced mobility passengers, on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

Pope Francis (C) boards his plane from a lift designed for the boarding and off boarding of reduced mobility passengers, on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

Pope Francis boards his plane from a lift designed for the boarding and off boarding of reduced mobility passengers, on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

Pope Francis (2nd L) boards his plane from a lift designed for the boarding and off boarding of reduced mobility passengers, on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

Pope Francis (2nd L) boards his plane from a lift designed for the boarding and off boarding of reduced mobility passengers, on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

An ITA Airways plane with Pope Francis onboard taxis on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

An ITA Airways plane with Pope Francis onboard is redied for take off on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)

Crew members wait for the Pope Francis to boards his plane on September 13, 2022 at Rome's Fiumicino airport, as he departs for a three-day trip to Kazakhstan. - Pope Francis, warned by doctors not to travel to Ukraine in the immediate future, will Tuesday bear a message of peace instead to a tense Central Asia with a three-day trip to Kazakhstan. The Argentine pope, who is forced by knee pain to use a wheelchair and has admitted he must slow down or consider retirement, will take part in an inter-religious summit in the capital, Nur-Sultan. (Photo by Andreas SOLARO / AFP)