Peel Group initially began a six-week analysis in July after claiming the airport "may no longer be commercially viable".
Local politicians in South Yorkshire urged the group to extend the deadline to the end of 2022 to help negotiate the sale of the airport.
Peel Group, however, said it would be "unsustainable" to extend the review by that much – but agreed to prolong it until 16 September.
A spokesperson told the BBC the airport board and its owner had been involved in "extensive engagement" with stakeholders to discuss the future of the business.
They said the extension had been agreed – "despite the lack of tangible proposals" from public or private sector partners – to allow more time for stakeholders to conclude their discussions.
