Saudi-Qatar flights resumed on Monday as the neighbors normalize ties under a landmark agreement that ended the Gulf row that erupted in 2017.
Saudi Arabia, the United Arab Emirates, Bahrain and Egypt in June 2017 severed diplomatic and economic ties with Qatar over its support for terrorism.
The quartet agreed to lift the restrictions at a Gulf Cooperation Council summit last week in the Saudi desert city of AlUla, after a flurry of diplomatic activity by outgoing US President Donald Trump's administration.
The first commercial flight between Qatar and Saudi Arabia in three and a half years, a Qatar Airways service to Riyadh, took off from windswept Doha airport around 1100 GMT and was due to touch down at 1210 GMT.
Airport staff filmed aircraft taxiing on the runway in anticipation of the departure, according to an AFP correspondent on the ground.
Economy tickets for flight QR1164 aboard an Airbus A350 were on sale for around $650 one way to cover the roughly 600 kilometers (370 miles) between the neighbors' capitals.
A Saudia Airlines plane will also fly Monday from Riyadh to Doha, departing the kingdom at 1340 GMT according to its online schedule, with services from Jeddah expected to start at a later date.
Just as the first flight to Riyadh was preparing to take off, Qatar Airways tweeted that services to Jeddah and Dammam would resume later in the week.
Bahrain and the United Arab Emirates have both opened their airspace to Qatari aviation under the deal but there has been no word on when the first direct flights will take off.