Starting 21 March 2018 onwards, all visitors to Oman will be required to obtain a visa in advance, rather than having the option of obtaining one on arrival.
This is in an effort to avoid the long immigration lines which are now forming at Muscat International Airport. The cost is not detailed as yet but at the moment a tourist visa valid from one to thirty days stay is priced at Oman Rial 20 which is approximately £40 per person.
Here are some instructions from Oman Air:
In continuation to ROP’s efforts to ease the visa process and the launch of www.evisa.rop.gov.om, it has been decided that effective 21st March 2018 all manual visa processes will cease and requests for Tourists, Express & Residence visa will be only processed through the above-mentioned website.