FlyerTalk Evangelist, Ambassador, British Airways Executive Club
Join Date: Jun 2008
Location: Somewhere between 0 and 13,000 metres high
Programs: AF/KL Life Plat, BA GGL+GfL, ALL Plat, Hilton Diam, Marriott Gold, blablablah, etc
Posts: 30,629
Some fares allow free stopovers, others do not. You need to look into the specific ticket rules of the fare you are seeing, but typically the cheapest fares do not allow any stopover at all. As mentioned by andset1191, your only way if you want to book on oe of the cheapest fares is a stop of under 24 hours which thus does not count as a fare. Also, be aware that with a stopover, taxes will go up quite significantly both because of extra airport taxes (standard) and because you become eligible to the British government air tax on the LHR-NYC segment.