A ceremony for the crash victims will be held in Tehran at 8:00 pm (1630 GMT) Tuesday ahead of processions in the capital on Wednesday morning before Khamenei leads prayers at a farewell ceremony.
Countries including Türkiye and Russia have announced they will send representatives to the funeral.
Raisi's body will be flown from Tehran to his home city of Mashhad in the northeast, where he will be buried on Thursday evening after funeral rites at the Imam Reza shrine.
Raisi, 63, was elected president in 2021. The ultra-conservative's time in office saw mass protests, a deepening economic crisis and unprecedented armed exchanges with arch-enemy Israel.
Raisi succeeded the moderate Hassan Rouhani at a time when the economy was battered by US sanctions imposed over Iran's nuclear activities.
Messages of condolence flooded in from Iran's allies around the region, including Syria, Palestinian militant group Hamas and Lebanese militant group Hezbollah, both of which are backed by Tehran.
It was an unprecedented Hamas attack on Israel that sparked the devastating war in the Gaza Strip, now in its eighth month, and soaring tensions between Israel and the "resistance axis" led by Iran.
Israel's presumed killing of seven Revolutionary Guards in a drone strike on the Iranian consulate in Damascus on April 1 triggered Iran's first ever direct attack on Israel, involving hundreds of missiles and drones.
In a speech just hours before his death, Raisi underlined Iran's support for the Palestinians, a centrepiece of its foreign policy since the 1979 Islamic Revolution.
Palestinian flags have flown alongside Iranian flags at ceremonies held for the late president.
Tribute was also paid to Raisi by a China-led regional bloc on Tuesday.
Envoys from Russia, China, India and Pakistan were among those who stood for a minute's silence at a Shanghai Cooperation Organisation summit in Astana, Kazakhstan.