How many blocks are there? 12. Blocks 1-8 are all MEM-based, non-instructor pilots; Block 11 is just instructors, Block 9 is just ANC base; Block 10 is just HKG base and Block 12 is just LAX base.

How are the block sizes determined? Blocks 1-8 are determined by seniority number. The others are apparent by their membership.

Are all blocks the same size? No. Blocks 1-8 have from 540 to 620 pilots in each; Block 11 has nearly 500; and the domicile blocks just have the population of that domicile: ANC=414, LAX=189, HKG=93.

Will more blocks ever be added? Don’t know.

Do pilots stay in the same block their whole career? Possible in theory (offered an assignment to HKG during new hire week then stay there until you retire). But in practical application, no, you don't remain in the same block your whole career.

Do you stay in your block regardless of domicile? See above.