PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - Whatever happened to the missing Malaysia Airlines Boeing 777-200 plane, it must have been extremely sudden because pilots have several ways of calling for help, said retired pilot Captain Lim Khoy Hing.

He said that they normally used VHF radio communication, which has a limited range of up to 402km.

For long distance communication, he said they used HF radio communication which had a much wider range of over 1,609km.

Another option was to use the Controller-pilot data link communication (CPDLC) to declare an emergency.

"In this case, the B777-200 is equipped with the CPDLC. The pilots would have been able to communicate and overcome range problems, so this tells you something must have impeded them from making the mayday call," he told The Star Online.

Captain Lim said that at the reported 35,000ft that the MH370 flight had lost contact, the pilots would need around five minutes to bring it down to a safe level of 10,000ft.

He said that at this height, passengers would not need to use an oxygen mask, adding that this would have also given the pilots time to make the distress call.

"Pilots are trained to make the mayday call as soon as they encounter an emergency. Everyone in the same airspace on the same frequency will hear it and the first priority will be given to the plane so it can land safely," he said.

Captain Lim, who has nine years experience flying the B777-200 model for MAS, agreed with American aviation experts interviewed on CNN that the aircraft's disappearance had happened during the safest point in the flight.

He said this was because of several factors, including the fact that it had been on cruise mode at a constant power and speed.

"The most dangerous points in a flight is the taking off and landing because there are so many variables present. In addition, the B777-200 is one of the safest because of its modern technology," said Captain Lim, who started his flying career in 1967 before retiring in 2011.