Q. Is it possible to make seat selections on a code shared flight well in advance (I'm making reservations 3-4 months before the travel date)? I really hate to get stuck in a lousy seat on a long flight or, believe it or not, separated from my wife.
A. Booking a codeshare flight is sometimes a great idea as it can lead to a lower price. Or it can be an inevitable choice when airlines cooperate and only provide one option in a complicated booking. But, seating choices are not lost; there are a few things to know.
First, whoever sold you the ticket (or whichever airline issued the ticket; indicated by the first three numbers of an airline ticket number), should be able to provide you with a record locator for the segment of the codeshare flight. It is often a different record locator issued by the airline that is actually operating the flight. Sometimes the issuing airline will say it is the same locator, but always ask again as it usually is different. With that information, simply call the toll-free number of the airline operating the flight and give them that information to choose a seat.
If for some reason, the issuing airline cannot locate a new record locator for the operating airline, then call the operating airline with the date, time, and flight information to assign a seat. With that said, many European and Asian airlines do not pre-assign seats for domestic or regional flights (especially in Economy Class although they do for long-haul flights). Business or First Class seating can usually be secured in advance (British Airways is a notable standout that charges for this service if the request is made more than 24 hours before departure).
It is always worth seeking out the record locators from each individual airline (do not assume they use the same one that your issuing airline gave you) and calling the operating carrier with your flight information to get seats. If traveling British Airways, either cough up the fee or provide your elite frequent flyer number with BA or with the oneworld alliance, which will allow you to pre-book seats free. And we're glad you and your wife are getting along so famously, even on those long and cramped flights.