Pope Francis, 87, was set to land in Muslim-majority Indonesia on Tuesday for a visit dominated by interfaith ties, the start of an ambitious four-nation tour that will be the longest of his papacy.

The pontiff left Rome on Monday afternoon and was due to land in Jakarta at 11:30 a.m., the first stop in a 12-day voyage that will also take in Papua New Guinea, East Timor and Singapore.

Covering about 32,000 kilometers (almost 20,000 miles), the tour — the longest and farthest of his 11 years leading the worldwide Catholic Church — will test Francis' increasingly fragile health.