A surge of no-frills seats at the biggest U.S. carriers potentially will backfire as passengers discover all the perks they’re giving up, said the chief executive officer of discounter Spirit Airlines Inc. Prohibitions on changing a reservation or bringing a roll-on bag may disappoint some customers of the new fares at American Airlines Group Inc. and United Continental Holdings Inc., Spirit CEO Bob Fornaro said Wednesday. While Spirit charges for carry-ons and even soft drinks, at least customers know what they’re getting, he said.