In 1998, Catholic-Muslim dialogue was initiated between Vatican experts and Muslim scholars of Cairo's al-Azhar University, the main center for Islamic learning for the more than 1 billion Sunni Muslims worldwide. The trip will come amid increasingly closer relations between the Vatican and al-Azhar, which is considered the most authoritative theological-academic institution of Sunni Islam. The pope has also said he sees the importance of strengthening cooperation between Catholics and Coptic Orthodox Christians in the face of so many threats to human life and creation.

Here is the pope's schedule as released by the Vatican. Times listed are local, with Eastern Daylight Time in parentheses.

Friday, April 28 (Rome, Cairo)

-- 10:45 a.m. (4:45 a.m.), Departure from Rome's Leonardo da Vinci International Airport for Cairo.

-- 2 p.m. (8 a.m.), Arrival at Cairo airport. Official welcoming ceremony at the Heliopolis presidential palace. Courtesy visits with el-Sissi and Sheik el-Tayeb. Speeches by the grand imam and the pope to participants in an international conference on peace.

-- 4:40 p.m. (10:40 a.m.), Meeting with local authorities. Speeches by el-Sissi and Pope Francis. Courtesy visit to Pope Tawadros. Speeches by Pope Tawadros and Pope Francis.

Saturday, April 29 (Cairo, Rome)

-- 10:00 a.m. (4:00 a.m.), Mass in Cairo. Homily by pope.

-- 12:15 p.m. (6:15 a.m.), Lunch with Egypt's bishops and the papal entourage.

-- 3:15 p.m. (9:15 a.m.), Prayer gathering with clergy, men and women religious, and seminarians. Speech by pope. Farewell ceremony.

-- 5 p.m. (11 a.m.), Departure from Cairo airport for Rome.

-- 8:30 p.m. (2:30 p.m.), Arrival at Rome's Ciampino airport.