Dear friends,
especially on business trips, you often must book your flight just a couple of days before the expected departure date and so the fares could be really high. In this case, it could be cheaper to book to separate round trips as per the following example.
From xxx to yyy.
Departure: Jan. 7th
Return: Jan 8th
Standard booking: 1 single round trip from xxx to yyy and return in the above dates.
Alternative options:
1 round trip from xxx to yyy, with departure on Jan 7th and return in any date that would allow you the best price.
1 round trip from yyy to xxx, with departure on Jan 8th and return in any date that would allow you the best price.
The alternative option, especially for short flight, could be cheaper than the standard way.
Now, sorry for the long introduction, let's go to my question: if you purchase two round trips, you remain with two unused tickets. What happen if you go to the airport when you are supposed to leave, complete the check-in and then you simply go away from the airport without boarding? Would you earn miles in any case? I am sure the airline would wait for you at the gate for a while but then they will let the plane leaving without you.
Does anyone has got any experience on this condition?

Bye.

Back to back ticketing is against the rules but you are unlikely to get caught. Checking in and not boarding will not get you miles. The plane will not wait for you.

The practise you are talking about with buying two tickets instead of one is pretty common and could save you money. I doubt they will wait for you at the gate if you check-in. But I don't see why you should check-in for a flight you are not going to take, you are only going to add hassle for the airline/gate-agent.

If you are concerned about getting caught, just book the two round trips with different carriers.

If you can plan your business trips well in advance, rather than "throwing away" the second legs of your round trips, book them for a tme when you think you might go back to that destination.

Seems pretty clear that the OP doesn't care if the plane waits on the 'throwaway' legs or not !!

To 'claim' the miles, you'd need to have the boarding pass scanned, or collected, or whatever. And hastily departing the airport from that situation would likely raise some eyebrows

About 'rules' -- if the fare rules have some minimum-stay requirement, that's one thing. But if not, and it's purely a matter of price -- then, why not ?
Note: you'll want to schedule those odd 'future returns' so they make a complete trip, right ???

Having two tix booked so as to avoid minimum stay requirements is a violation of the ticketing rules, and the carrier can refuse you the miles, refuse to carry you, try to make you pay the "real" fare, or cancel your FF account. While others are correct that you are not likely to get caught if you do it infrequently, you probably will if you do it a lot, and that defeats the purpose of earning the points in the first point.

To the OP, you will definitely not get the points for the throw-away segment(s), regardless of whether you have checked in online or not. If you're not on the plane, you get nothing.

S.

If you don't show up for the first leg of an itinerary, I believe the rest of the legs become invalid. Therefore you won't be able to use the return ticket on an itinerary where you didn't first use the outbound ticket.

Checking in but not boarding does not count as having used the outbound.