The original 707-100 had the non-fan JT-3(J-57) engine and didn’t quite have the range for reliably non-stop London-New York flights but was OK non-stop NY to LA. (Many were later re-engined with JT-3D turbofans)

Air-India and BOAC had the bigger Intercontinental model and theirs, (-400s) ,had the RR Conway engine which was briefly the best option around 1960/1961, gave reliable London-New York non-stop range but not US West coast to Europe non-stop.

The 707 Intercontinental was developed into the 707-320B/C of 1962 which had the JT-3D turbofan and improved wing which gave it the ‘6,000 mile’ range to fly US West Coast to Europe non-stop with a useful payload

The 707-100 was designed to satisfy the 4,000 mile range market. This increased with the JT3 engines over 6,300 miles with later versions (max fuel). Air India and BOAC were equipped with the -400 series which had the greater range.

Operational considerations; full load will reduce range and there may be passenger drop/collect options in the 1960s.

London to Bombay (as was) is 4400 miles great circle, so actual flown will be more. I can see at least one stop required, and the schedules of that time indicate that.

DAI