The Istanbul-based company last month signed a three-year, 3 million euro sponsorship deal with European chamnpions Barcelona as it seeks to become a global brand.
Details of the deal with United were not disclosed.
"This deal is yet another indication of the global appeal of Manchester United and we are very pleased to welcome them (Turkish Airlines) to the club," United chief executive David Gill said in a statement on the club's website.
Under the terms of the deal the airline will fly the team's players and officials to relevant matches, tournaments and training camps as United's official carrier.
The English champions said on Wednesday they were more than $1 billion in debt.
Debts at parent company Red Football Joint Ventures Limited hit 716.5 million pounds in the year to June due in part to high interest payments, its accounts showed.
Accounts for the holding company showed the debt had risen by 17 million pounds in the year. Net interest for the period was 68.5 million pounds.
The debt figures overshadowed profit of 6.4 million pounds for the financial year, compared to a loss in 2008 of 42.7 million pounds.
In 2009, United won the league title for the third consecutive season and lifted the League Cup but lost the Champions League final to Barcelona.
The Manchester club's finances were also boosted during that time by the sale of Portugal winger Cristiano Ronaldo to Real Madrid for 80 million pounds.
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