Boston to New Delhi India with a long layover in London $550 RT on Virgin Atlantic (travel Apr, May & Jan) 2-Trips-In-1 (other US Cities available as well)

edit to add: this deal is also available out of New York, Miami, Washington DC, Los Angeles and San Francisco and for September 2017
Virgin Atlantic, via Priceline, have roundtrip airfares travelling from Boston (BOS) to New Delhi India (DEL) for $550 including taxes and fees. This makes 1 stop in London Heathrow and possibly up to 22 hours, ymmv, depending on the flight you chose. This makes for a great two-in-one trip even if it’s just for a day in London. Even if you don’t want to explore London, this is a great price to India on a great airline!
Departs BOS: Apri 24-26; 28-30; May 1-5, 6-10; Jan 11, 12, 13, 17, 18, 19, 20, 2018
Returns BOS: May 2-6, 8-10, 12-14, 28-30; Jan 14-23, 2018
This will price $566 on Virgin Atlantic. Use Priceline and it will reprice it down to $550. See sample travel dates below.