Ok to Board (OTB) is a visa verification process required by airlines flying to the UAE. It involves the airline checking the authenticity of the passenger's UAE visa and updating their reservation with a visa clearance message. Without an OTB update, passengers will not be allowed to board their flight. The visa sponsor must submit the visa copy and ticket to the airline office, who will verify the documents and insert the OTB status into the passenger name record (PNR). Passengers can then check their OTB status directly with the airline prior to departure. Certain airlines like Emirates provide free OTB updates due to relationships with sponsors.