Regarding points raised by SeeBuyFly:

1) As most people might already know, legality of ability to stay in US is governed by date stamped by immigration officer, US visa is useless once legal entry into US is completed. Now assuming situation where OP is returning from JFK to BOM via LHR before expiry of I-94 but after original visa has expired, does OP really need UK transit visa? (Doesnt make practical sense. What happens if UK denies transit visa. Wait until US forcefully deports you?)


2) IMHO, practical data-points from "random" people (neither Keyser nor B747 can be called random though )) are LOT MORE useful and reliable than official web-sites from real world situation point of view. In fact, thats why most of us post queries here. (Trying to reach airline call centers and then trust their answer may not be advisable in such complicated issues)