These days, especially with international travel, a number of new discount carriers and special fares mean that it’s often cheaper to use two tickets to a destination.

In fact, in some cases, it’s the only alternative, when one of the airlines involved is an internet-only airline, or has no “ticket agreement” with the first or over-water carrier.

In other cases, the two airlines may have a “ticket agreement “(translation, they can be put together on one ticket), but they may not have a “joint fare” (translation, one fare all the way through to the final destination).Or the “joint fare” may be much higher than issuing two tickets.

Travel agents issue separate tickets all the time in this scenario, and savvy internet shoppers may put together a bargain priced itinerary using multiple airlines and tickets. But there is a risk. It doesnt just involve luggage and/or missed connections, although that could happen too. It involves schedule changes, and it could mean paying a lot more before you even get to the airport.

Even with two airlines on one ticket, and even when they are code shares — British Airways-American, United-Continental, and Delta-KLM, for examples — it seems as if any problem automatically triggers the blame game. Airlines love to claim it was someone else’s fault.

But when the tickets are issued separately, airlines will not only blame each other, they will deny all responsibility, even with plenty of advance warning.

My most recent case involved an itinerary with United Airlines and Mongolian Airlines, where there was, not surprisingly, no good business-class fare all the way to Ulan Bator. But there was a good business class fare to Seoul, with a six-hour connection, and then a flight on to Mongolia. There was a similar connection on the return. So, even if the flights were late, it wasn’t going to be a problem. In theory.

The flights were scheduled for mid-April, and ticketed in mid-February. But about 10 days after ticketing, Mongolian Air changed some of their daily flights from Ulan Bator to Seoul from 6:45 a.m., to 1:05 p.m., which meant that my client’s six hour connection not only disappeared, but became a complete misconnection, as the new flight now arrives ten minutes after her United return flight was scheduled to leave.

Since Mongolian Air is keeping their morning flight three days a week, it was a relatively simple thing to adjust the trip by a day, which would allow the connection to work. But United has a $500 change fee for their discount business class fares. Since the flights were on the same record, I decided to call and ask what we could do.

The answer — basically nothing. The first agent I asked said, yes, I can see that the connection is now impossible. When I asked if United would waive the penalty to change the flights to make the connection, she said, “No, it’s not our problem.” Literally. And when I said, but since you can see the issue and the flight on the next day is wide open would you consider helping her out? “No, it is not our responsibility, you didn’t issue one ticket.”

I tried, nicely, to tell the agent that there was no fare we could have used all the way to Mongolia. With no cooperation, I said, “Okay, thanks.” I told the agent I would see if our sales office could give us a waiver and hung up and called the sales office.

By the time I got through to the sales office, the (offshore) agent had gone so far as to document the record “Next agent, there is NO EXCEPTION for other airline schedule change.” Indeed, the sales office said that the penalty was absolute. Although they did let us reduce it somewhat by taking money out of a limited fund we have for such cases.

Now, I completely understand that airlines are in in the business of making money (not that they are all that good at it). But in this case, with wide-open flights and an obvious situation, it would have been trivial for United to waive the penalty. (Who knows, next time it could be THEIR schedule change.) But that’s not their policy.

The lesson perhaps for other travelers is that this wasn’t that difficult a situation to fix. It was well in advance and there were plenty of seats available. Just imagine if it were last-minute or during travel. (In this case, the client’s corporation was willing to absorb the cost, since there are few alternative flight options.)

Had the schedule change been a day or so before the flight and had the alternate return flight been sold out, or had it been a delay during travel; the cost and hassle factor could have been far greater.

This example is not to say that booking multiple tickets is a bad idea. The only available itinerary my client could have used with a single ticket would have been thousands of dollars higher. Alas, within Europe especially, separate tickets for internal flights are the only way to keep costs reasonable.

But on the other hand, travelers who do take advantage of such ticketing deals should keep close watch on their schedules to make sure they are current with all changes. Be prepared to be proactive and if necessary be ready to spend money. (Travel insurance is a possibility, but very few policies cover “for any reason.” So anyone looking for schedule change insurance will have to be very careful.)

If something happens with a schedule change or delay during travel, the best recourse is probably to acknowledge the airline’s policy and see if they will make an exception. If not, to write to customer relations after the fact for either or both airlines involved, explaining the extra out-of-pocket costs and seeing if they will issue a voucher or any compensation.

In future, consolidation in the airline industry may help with some of these problems, as code-share airlines actually merge or form overseas joint ventures. On the other hand, given the increasing numbers of small discount carriers, and the industry’s proclivity for ever increasing fees and penalties, the “not our problem” schedule change will most likely become increasingly a traveler’s problem.