Work colleagues Christopher Ringland and Christopher Holtom were on board the Turkish Airlines flight from Istanbul, when it came down in dense fog, killing 75 people.
The pair, both employees of Mirlees, in Stockport, Greater Manchester, were planning to visit a power station in Turkey.
"
They should never have taken off in that fog - it was so
thick
"
Rita Holtom, mother of victim Christopher Holtom
Two other men, David Hastie, of Baillieston, Glasgow, and Muhammed-Nazmul Haque, of north London, are also missing, presumed dead, the Foreign Office has confirmed.
Only five people are thought to have survived after the plane crash-landed onto a field near Diyarbakir Airport on an internal flight from Istanbul on Wednesday.
Christopher Ringland, 31, from Manchester, was due to get married in June. He was described as "a popular guy".
His colleague Christopher Holtom, 39, had been on a two-week break following a knee operation and was not due to be back at work until Monday.
His mother Rita said he was asked to return early by his company to join Mr Ringland on the business trip.
She said: "We just can't believe it. You think that your children are always going to out-live you."
She said Christopher, who was married with a young boy of his own, was "a lovely son".
She added: "They should never have taken off in that fog - it was so thick."
Mr Ringland's sister, Claire, 19, from Denton, Manchester, described him as a "nice, kind, generous man" who meant everything to the family.
She said: "It's not sunk in yet and it won't for a long time. We're all so numb. Christopher was such a popular guy."
'Bad weather'
At Mr Hastie's home in Scotland, neighbours expressed their shock at his death.
Retired lorry driver John Watson, 72, said Mr Hastie was a geologist who specialised in oil exploration.
He had recently become engaged.
"He was a thorough young gentleman and a good neighbour and will be sadly missed," said Mr Watson.
Flight TK634 hit the ground 30m short of the runway just after 1700 GMT.
There is no firm indication yet what caused the crash, but Turkish Prime Minister Abdullah Gul said it was probably due to bad weather.
Helpline
Witnesses say the plane split into two and then burst into flames, spraying debris over a large area.
Of the people who survived - including a young child - most are said to be in a serious condition.
The BBC correspondent in Turkey, Jonny Dymond, says this is the worst plane crash in Turkey for more than 25 years.
The spokeswoman for Turkish Airlines said: "Turkish Airlines expresses its deep condolences for the ones who lost their lives in the sad accident and we wish urgent recovery for the survivors."
A hotline had been set up by the Turkish authorities for concerned members of the public on 00 902 12662 5300 or 5301.