Originally Posted by
ATOBTTR
No, they won't. Their systems do not "talk" to each other in this regard. That said, if you made a habit of it, the airlines could suspend/terminate your FF account as "speculative bookings" are against COC rules and while happening in small numbers won't set off flags, making a habit of it could.
On a similar note, what you can do is use two different airlines to circumvent fare rules too. Airline policies prohibit "nested ticketing" with the purpose of circumventing fare rules. I.e. say you had to travel AAA-BBB and back two weeks in a row, traveling on Mondays and Fridays, for simplicity sake, we'll say on the 1st and 5th and then again on the 8th and 12th. The airlines wanted you to book it as AAA-BBB-AAA on the 1st through the 5th (Monday through Friday) and then a second ticket for AAA-BBB-AAA (Monday through Friday) on the 8th and 12th because in both cases, neither fare would come with a Saturday night stayover and thus was usually more expensive. What some people would do was book AAA-BBB-AAA outbound on the 1st and returning on the 12th that had a Saturday night stayover with a nested ticket of BBB-AAA-BBB on the 5th through the 8th as a Friday through Monday with a Saturday night stayover, with the purpose of getting cheaper tickets because both fares now had Saturday night stayovers. The airlines considered (still consider) this a prohibited practice and could catch it if you had both tickets on the same airline. But what they couldn't prohibit (or track) was if you did the latter across two different airlines.
Domestically in the US this has become less of an issue because now a lot of fares are simply a combination of one-way fares (you can now often see it's the same price to book two one-ways versus one round-trip - this wasn't always the case). But for international travel, many fares still have Saturday night stayover requirements for a cheaper fare so this could be an option for those with frequent enough travel though there is the risk of what you will need to do if one trip cancels.
This is great information! Will definitely come in handy for me. Thank you very much.