Authors, if there's a different posting of it you'd rather be linked, or if your anon posting on the meme has since been reposted under your name, please let me know and I will redirect it.
A Christmas Carolyn by tiwtin
Summary: A re-telling of Dicken's "A Christmas Carol"
(Carolyn makes a fine Scrooge.)
None So Blind by linguini17
Summary: Douglas becomes telepathic for a day and is determined to fix what he hears.
(Magic Reality AU. Heartbreaking in unexpected ways. Angsty and a bit dark in spots)
A Worthy Regard by Branwyn on AO3
Summary: People don't flinch from their parents that way unless there's good reason.
(Gordon Shappey turns up unexpectedly, harassing Arthur, and is dealt with by
A Short History of Aviation by loneraven
Summary: All Martin ever wants to do is fly. Four failed sublight qualification attempts, a murderous asteroid field and the world's cheeriest empath make this a little more difficult than he'd like.
(Star Trek AU. Not exactly a crossover, more of a blend. I wasn't sure how this would work, but it did, brilliantly.)
Wibbly-Wobbly Planey-Waney by an Anon on the Cabin Pressure Comment fic meme
First line of Prompt: Martin grew up in the TARDIS.
(Crossover with Doctor Who, Eleventh Doctor. This is, by turns, adorable, hilarious and enthralling, and the ending hit me right in one of my favorite tropes.)
Cairo by an Anon on the Cabin Pressure Comment fic meme
Prompt: It's been a miserable stressful flight, everyone is sniping at each other, the hotel's lost one of the room reservations, all four of them have to spend a miserable night in one small cramped room, still snapping at each other. ...That's when the pillow fight breaks out.
(Gen bed sharing and a pillow fight, and snark and all things wonderful.)
Some Things Don't Need Fixing, Just Good Company by c3mf
Summary: There's nothing a good cuppa can't help... until it can't. Then you resort to Plan B.
(A rare and quite genuine Douglas and Arthur friendship fic.)
Little Things (Make All The Difference) by c3mf
Summary: Five times the MJN crew performed awkward minor grooming on each other and one time it wasn't awkward at all.
(The MJN family at its most awkward, and its most badass.)
In Memory of Flight by lady_t_220
Summary: Douglas is familiar with the concept of the ghost in the machine. In fact, he's actually rather fond of it.
(AU - Martin is a ghost. This is touching and sad, and badass, and brilliant.)
The Care and Feeding of Your Resident Pilot-Ghost by alienstars2004
Prompt: Martin's students are actually very protective of their quiet pilot in the attic. So much so that the first generation of students added an extra clause to the student accommodation agreement based soley on the care of their house ghost: feeding him, fixing his van, helping him keep his accommodation. The second generation add more rules. And so do the third. All follow them without thinking.
(Full of funny and aww.)
Luck's Labor's Found by in_lighter_ink
Summary: There is a reason Martin has such bad luck: he takes the bad luck from others and makes them have good luck instead. Arthur realizes this and decides to try and give Martin all manner of good luck charms to try and help him keep a little luck for himself.
(Another lovely bit of magic realism.)
Tumble by Polite_Warning on DW
Summary: Martin Crieff sat in a van. Martin Crieff was such a sad man. As the storm started a rumble, he took a great tumble, and following, he had no plan.
(Martin whump, of the vehicular accident sort.)
Not an exhaustive list, just a smattering, there's loads more out there.