I am traveling with family on international itinerary. I hope to get upgraded as a CP. So far there are seats and I've had good luck going to this destination in the past. However, this year I have a new baby and did not purchase him a ticket, instead I will pay the 10% lap infant charge.

The problem is that for some ridiculous reason, US Air does not let you do OLCI if you have a lap infant. Which hurts your chances for upgrade since I can't be first to check-in if there are other CPs on the flight.

So... solution is to wait until after OLCI (24 hours before departure, on the phone) or at the airport to buy the ticket. Will they charge me 10% of the current fare or 10% of my fare? I suppose there's a chance the current fare at day-before travel could be quite high ($3000 or more). Also what if the plane is sold out? That shouldn't matter (he's on a lap) but who knows.

Separately, can I buy him a one way lap infant fare then buy the 2nd one (return fare) at the airport on the way back? That way I can OLCI for the return flight, too.

In the past, on roundtrips, whenever I have a lap infant domestic they always add him to the return automatically. But I guess if I just pay for one way they will only give him a ticket for that way and I can just show up at the airport and pay the 10% on the return.

Ideas? My goal is to (1) preserve OLCI in both directions; (2) pay as little as possible for the lap infant, but a small price increase if #1 is preserved is fine; and (3) not do anything crazy to jeopardize the whole trip or cause any huge problems.