When my husband accompanies me on a business trip, I have to go through a messy process to book plane tickets. I'm required to use the company TA's site for my flights and forbidden to use it for anyone else's. So, I flip back and forth between 2 browser windows till I find a flight I can take and that has reasonable airfare for my husband. (On domestic travel, the TA usually gets the same cost as the airline's site before the TA adds on their $25 "booking fee. But I digress.)
Then I hit "Purchase" on both, select seats and call the airline to have the records linked. Somehow I messed up once and booked my flight home leaving a day later than his. He was booked to leave on the correct date. So, I called the airline, begged for mercy and was let off with a change fee but no additional airfare.