[UPDATE, April 1, 6:29 p.m. EDT: Delta now says that while "end-on-end combinability of non-refundable fares has been restricted," booking within one passenger name record "multiple one-way tickets for the purpose of constructing legitimate circle trips" is again possible. "You can book any one-way ticket we offer for sale, but we do not recommend using multiple one-way tickets to create connecting itineraries," the airline added. "It increases . . .