Asobo doesn’t give a single (care) about the functionality of Achievements in the sim and I’ll die on this hill. It’s so ridiculous.
To date, Xbox users have had TWO out of the ten “weekly challenges” needed for the Decathlon Achievement.
Landings are failing to register in the logbook.
Flight time fails to register in the logbook.
“Completionist” is still broken.
Btw: assuming the achievement hasn’t been broken by an update, you don’t need to go gate to gate. You can take off from your runway of choice at LFBD and the Achievement should pop before you’ve finished your roll after arriving at KSEA.
Good luck.