My travel airlines, how do i pre book which seat i would like to sit in on my flight. to mexico in sept 06.?

My husband and i have booked a holiday to mexico in sept 06 flying on amy travel flight, and wish to be seated at the back of the aircraft on 2 seats window seat. how do i do this i no this will probably incurr an extra cost.
Answer
Depends on how you booked. if you have the airlines record locator number, go to their website and put in your reservation. you can pull up the seat map to see if there is anything else available. this far out, you should be able to move seats. some airlines only charge for premium seats, like the exit rows and a few rows in the forward part of the cabin. some airlines are now charging for aisle seats if you request one. moving seats in general does not cost. just remember a pre-assigned seat is just a request, not a guarentee. the airline between now and then can change the aircraft to a larger or smaller one and they do an automatic reseat. always check the airline for the flight schedule a week or a few days before departure. flight numbers and schedules change seasonally and what you booked now can change between now and then. august is usually when they put out the new schedule for the fall, so make sure you stay aware of any changes. you can call the airline directly, or go to their website.