Interpol, which released pictures of the men, said the two men travelled had travelled from Qatar's capital Doha to Malaysia on their Iranian passports, then apparently switched to the stolen Austrian and Italian documents to board the Malaysia Airlines flight.
Interpol secretary general Ronald Noble said the latest information about the men made terrorism a less likely cause of the plane's disappearance.
He identified the men as Pouri Nourmohammadi, 19, and Delavar Seyedmohammaderza, 29 who boarded the plane together.
Malaysian police chief Khalid Abu Bakar said the teenager was planning to enter Germany to seek asylum. Mr Khalid said: "We believe he is not likely to be a member of any terrorist group."
He said the young man's mother was waiting for him in Frankfurt and had been in contact with police. Mr Khalid said she contacted Malaysian authorities to inform them of her concern when her son did not get in touch with her. Both men had onward tickets to European destinations.
The developments came as Malaysia's military said it believed the jetliner missing for almost four days had turned and flown hundreds of miles to the west after it last made contact with civilian air traffic control.
A massive search operation for the Malaysia Airlines Boeing 777-200ER has so far found no trace of the aircraft or the 239 passengers and crew.
Malaysian authorities have previously said flight MH370 disappeared about an hour after it took off from Kuala Lumpur for the Chinese capital Beijing.
But a senior military officer, who has been briefed on the investigation, said: "It changed course and took a lower altitude. It made it into the Malacca Strait."
That would appear to rule out sudden catastrophic mechanical failure, as it would mean the plane flew about 350 miles at least after its last contact with air traffic control, although its transponder and other tracking systems were off.
The Strait Of Malacca, one of the world's busiest shipping channels, runs along Malaysia's west coast.
A Malaysian newspaper quoted air force chief Rodzali Daud as saying the plane was last detected at 2.40am on Saturday by military radar near the island of Pulau Perak at the northern end of the Strait of Malacca.
It was flying about 1000ft lower than its previous altitude but there was no word on what happened to the plane thereafter.
The effect of turning off the transponder is to make the aircraft inert to secondary radar, so civil controllers cannot identify it.
Police had earlier said they were investigating whether any passengers or crew on the plane had personal or psychological problems that might explain its disappearance, along with the possibility of a hijack, sabotage or mechanical failure.
There was no distress signal or radio contact indicating a problem and, in the absence of any wreckage or flight data, police have been left trawling through passenger and crew lists for potential leads.
Malaysian police chief Mr Bakar said: "Maybe somebody on the flight has bought a huge sum of insurance, who wants family to gain from it or somebody who has owed somebody so much money, you know, we are looking at all possibilities."
A huge search operation for the plane has been mostly focused on the shallow waters of the Gulf Of Thailand off Malaysia's east coast, although the Strait Of Malacca has been included since Sunday.
Navy ships, military aircraft, helicopters, coastguard and civilian vessels from 10 nations have criss-crossed the seas off both coasts of Malaysia without success.
The massive search for the plane has drawn in navies, military aircraft, coastguard and civilian vessels from 10 nations.
China, where two-thirds of the passengers are from, urged Malaysian authorities to "speed up the efforts" to find the plane. It has sent four ships, with another four on the way.
Assuming the plane crashed into the ocean or disintegrated in midair, there will likely still be debris floating in the ocean but it may be widely spread out, and much may have already sunk. In past disasters, it has taken days or longer to find wreckage.