Bob Woodruff, an ABC News correspondent, obtained a copy of an email the man said he sent to his employer stating he witnessed the crash.

“I believe I saw the Malaysia Airlines plane come down. The timing is right,” the man said in the email. “I tried to contact the Malaysian and Vietnam officials several days ago. But I don’t know if the message has been received.”

According to Woodruff, Vietnam officials confirmed they received the email.

In the email, Michael McKay describes what he believed to be a plane burning at high altitude, about 50 to 70 km away from his location.

McKay said while he “observed the burning (plane), it appeared to be in one piece.”

The oil rig worker provided GPS coordinates of his location and an approximate location where he saw the plane.

“From when I first saw the burning (plane) until the flames went out (still at high altitude) was 10 to 15 seconds,” he wrote. “There was no lateral movement, so it was either coming toward our location, stationary (falling) or going away from our location.”

The ongoing multinational search for the missing plane now includes roughly 43 ships and 39 aircraft from at least eight nations, according to Malaysian Defence Minister Hishammuddin Hussein.

With a search operation of this magnitude Captain Rick McClure, an air coordinator with the Joint Rescue Co-ordination Centre Victoria (JRCC), said the challenge of finding the aircraft grows with each passing day.

“If something goes down in the water that area you’re searching gets bigger everyday because of drift. It’s a tremendous challenge,” said McClure. “If things went ideally you’re looking for a life boat. But the reality of a plane going into the water is you’re looking for an oil slick or a pool of gas or things that float.”

McClure said search teams looking for floating items like ceiling tiles or seat cushions are battling against ocean currents that pull debris fields apart requiring search efforts to widen.

Currently, search teams are scouring approximately 92,600 square kilometres hunting for any signs of Malaysia Airlines flight 370.

McClure said search efforts are also hampered by the thousands of tips and reports flooding in from the public. The huge volume of responses requires an equal amount of manpower to assess each statement.

“You have to talk to the person, how they sound, how believable they are. What specifically they were doing,” said McClure. “Most of (the reports) aren’t valid, but you have to sift through them all.”

McClure said valid reports tend to have “specific details” and create an imprint in the minds of witnesses.

On Wednesday, Malaysian officials were exploring the possibility the jetliner, carrying 239 people, may have attempted to turn back before it vanished from radar.

Authorities began their search for the missing aircraft at the position it was last reported to be over the sea between Malaysia and Vietnam. But they have also said search operations were ongoing in the Malacca strait.

 With no debris found yet, authorities have not ruled out any possible cause, including mechanical failure, pilot error, sabotage or terrorism. (Toronto,  Global News)