Three Singapore Airlines (SIA) flights yesterday - two to London and one to Frankfurt, Germany - had to stop halfway for refuelling after the airline re-routed flights to Europe to avoid Pakistan airspace.
This was necessary as the decision to re-route added flying distance and time to the flights.
The refuelling was done in Mumbai and Dubai.
Confirming the diversions, SIA said that as a result of the delay to the Frankfurt flight, the return flight SQ325 was cancelled and the passengers were transferred to other airlines.
"All other flights that overfly the affected airspace will be re-routed, but are due to operate as scheduled at this point," the airline's spokesman said.
Pilots said this could add a few extra hours to flights.
The changes were made after India and Pakistan closed some of their airspace amid escalating tensions between the two countries.
The Straits Times understands that all Singapore-Europe flights, including those operated by other carriers such as Australia's Qantas, are affected.
While flights should depart Changi Airport on time, some delays are expected for flights arriving from Europe.
In a notice on its website, SIA said: "As the situation remains fluid, customers are advised to check the status of their flights on our website or contact their local SIA reservations office."
Customers are also advised to update their contact details here to receive updates on their flights.
SIA's budget arm Scoot also cancelled its flight to Amritsar in north India yesterday.
A Scoot spokesman who confirmed this said that the situation is fluid.
According to flight tracking website FlightRadar24, airlines are flying farther south over the Arabian Sea, Gulf of Oman and Persian Gulf to avoid Pakistan airspace.
SIA and Scoot are among many airlines affected by the airspace closure, which affects all services between South-east Asia and Europe.
Mr Albert Tjoeng, Asia spokes-man for the International Air Transport Association, told The Straits Times that there are about 220 flights operating between this region and Europe every day.
"Alternative routes are available for the flights impacted by the closure of Pakistan airspace," he said.
Defer non-essential travel: MFA
Singapore yesterday noted with deep concern the escalating tensions between India and Pakistan, and called on both sides to ensure the safety of all civilians.
A statement from the Ministry of Foreign Affairs (MFA) advised Singaporeans to defer non-essential travel to Jammu and Kashmir in India, and to Pakistan. "Travellers should also exercise precaution in other areas, especially the border regions between Pakistan and India, given the uncertain security situation," it said.
Several cities, including New Delhi and Mumbai, and the border districts of Kutch, Banaskantha and Patan in Gujarat, have been placed on high alert.
The statement also noted reports of airport closures and flight cancellations in various Indian states, including Jammu and Kashmir, Punjab, Himachal Pradesh, Rajasthan and Uttarakhand. And in Pakistan, MFA said, the Civil Aviation Authority has closed its airspace to all commercial flights, and there have been reports of flight cancellations across Pakistan.
"Singaporeans who are already in India and Pakistan should take all necessary precautions to ensure their personal safety. They are advised to stay vigilant, monitor developments through the local news and heed the instructions of the local authorities," the statement said.
"Do stay in touch with your family and friends in Singapore so that they know you are safe," it added, and encouraged Singaporeans in these two countries to eRegister with the Ministry of Foreign Affairs at https://eregister.mfa.gov.sg.
It added that those who require consular assistance can contact the Singapore High Commission in New Delhi on +91 11 4600-0800 and on +91 98102-03595, or through e-mail at firstname.lastname@example.org.
In Pakistan, there is the Singapore Honorary Consulate-General in Karachi, which can be reached on +92 21 3568-6419 and on +92 21 3568-5308, or through e-mail at email@example.com.
MFA also listed the Singapore phone numbers of its 24-hour MFA Duty Office: +65 6379-8800 and +65 6379-8855.