BMI is Heathrow's second biggest airline
UK airline BMI has declined to comment on newspaper speculation that it has been approached by Abu Dhabi carrier Etihad over a possible merger.
Etihad first went to BMI in the summer over a potential deal which values BMI at £600m, the Sunday Times reported.
The Middle East airline is also said to have spoken to Germany's Lufthansa, which owns a 30% stake in BMI.
Etihad said it had had "a number of discussions with a variety of carriers" but "no firm talks planned".
BMI operates more flights from London's main Heathrow Airport than any other airline except British Airways.
Like almost all airlines, BMI has seen its profits trimmed this year by the continuing high price of aviation fuel.
This has led to a number of carriers seeking closer ties with rivals, such as British Airways plans for a tie-up with American Airlines.
Other carriers have faced financial problems, such as Italy's Alitalia, which is trying to secure a rescue deal.
BMI flew 10.6 million passengers last year, and operated 70 aircraft.