Traveler's Aide: How early should you arrive for a domestic flight?

— -- Question: My family planned a vacation in Honolulu, flying from Houston at the end of July. We arrived at the airport and were in line by 8 a.m. Our flight was at 9:30 am.

There was quite a long line at check-in and we were concerned about how things were moving. My wife spoke to a Continental agent who told us we had to wait in line. By the time we got to the front it was 9 a.m. and the agent at the counter said we could not check in for our flight.

We had to rebook for a flight the next day and were charged $75 extra per ticket. Without any other options, I agreed to this under duress. I felt this was unfair to charge us for several reasons. We were in line to check in 90 minutes before the flight. We told a Continental agent of our concern and she did nothing but later, after we missed our flight, this same agent went through the line, bringing people with earlier flights to the front.

I have written two messages to Continental via its website with no response. I would like the airline to refund the $75 per-ticket fee because I feel we could have easily made our flight had the agents done their jobs.

— Son Tran, Houston

Answer: The Tran family's Houston-Honolulu misadventure was a cascade of shouldn'ts: They shouldn't have gotten stuck in a line, they shouldn't have been rebuffed by a check-in agent when they asked for help and they shouldn't have had to pony up $75 per person in fees.

Continental's terminal C in the Houston Intercontinental Airport reopened in May 2010 after a $65 million renovation. The new check-in area sports 115 check-in positions, with 56 self-service kiosks as well as full-service counters. Agents normally work in front of the kiosks, not behind them, and roam the area to assist people with questions and problems and to provide baggage tags.

The increase in Terminal C's check-in options is supposed to cut down on wait times, so travelers like Tran shouldn't get stuck in long lines. Waits at the Houston airport typically don't exceed 30 minutes, according to Continental representative Mary Clark.

Passengers must complete the entire check-in process, including checking any baggage, before the cutoff time, which varies by airport. The cutoff ensures there's enough time for both passengers and baggage to be processed, screened and loaded onto the aircraft.

In Houston, the cutoff is 45 minutes before the scheduled departure for domestic flights. That doesn't mean getting in line 45 minutes before your flight, but walking away from the check-in area with your boarding pass in hand then. During peak travel times, the airline recommends allowing a minimum of 60-90 minutes to allow enough time to pass through security as well. Peak travel isn't just major holidays, but also certain times of day when more people travel, including the window from 6:30 to 9:30 a.m., when the Trans were at the airport.

That said, Tran and his family did allow enough time under those guidelines, and they still missed their flight. It's unclear why the family had to wait about an hour in line before checking in for their flight to Honolulu and why the agent they spoke with didn't expedite them through the line.

"Our records don't show any reason for a longer line than normal that day," says Clark.