Lets get real here. No train is going to take less than 60 mins to travel from Manchester to London approx 200 miles. If there was enough runway capacity at LHR a flight from Manchester should not take much than 45 minutes chocks to chocks.
For passengers travelling between Manchester and London it becomes a choice of what is more convenient. For a passenger in transit to an onward destination the airplane is the obvious choice.
Once/If the HS2 is approved between Manchester and London there will be very few alternatives to fly anywhere, other than point to point short haul / lo cost carriers catering for the masses.
The major revenue like it or not is generated from the south east and the Home Counties, nothing is about to change in the immediate future.
Yes Emirates Qatar and Teahad all doing very well out of Manchester all concentratiting on volume and feeding their hubs for onward connections.
The problem Manchester has is the same problem from 30 years ago, the airlines make more money per flight from LHR than they do from Manchester. Nothing in the foreseeable future changes this.