However, is 3 flights a week profitable?
Probably not, but VS needs to understand that they are guests of Air India to use any of these frequencies. They are not entitled to them as per the bilateral. Branson came up with a brilliant idea to reverse-codeshare these unused frequencies and presented it to Air India, who saw the benefits and agreed to HIS terms. Branson personally was in Delhi to negotiate this agreement and of course pulled a PR prank when he was there too by alleging that BA had denied him boarding to get back to London - the truth was that the flight was oversold and they simply refused to sell him a revenue ticket since they were already sold out. The terms were for 2 initial weekly frequencies, plus a third frequency CONTINGENT upon AI being awarded additional slots at LHR for their own operations. The AI slots never materialized and hence the third frequency didn't materialize. Rather than approach the Indian Government and REQUEST the third frequency anyway, VS instead chose to serve a termination notice and THEN publicize their pullout "because 2 frequencies are not sufficient". Well guess what buddy, if you wanted more frequencies, it might have helped if you had asked.
Air India is perfectly happy to give VS more service on dormant DEL-LHR frequencies (forget about BOM though, that is a fortress that even a Virgin won't be allowed near) as long as they get their codeshare block on the flights as well. In the end it allows AI to gain incremental revenue at virtually zero cost, and more importantly to both VS and AI, it weakens BA's market share to/from India. However, the Indian government will not (nor should they) capitulate and give VS their own rights to fly to India as long as the Indian flag carrier is denied Heathrow access for already awarded but dormant frequencies.
"The A340-300 may boast a long range, but the A340 is underpowered" -- Robert Milton, CEO - Air Canada