Flightline is the second of four racing-age foals and the only stakes winner out of Feathered (Indian Charlie), a Graded winner at Grade 3 level and three times placed in Grade 1 company. His half-brothers include Good On Paper (War Front), a winner in the US, and Voron (Pioneerof the Nile), a winner in Russia.

Second dam Receipt (Dynaformer) was stakes-placed and had three winners, Feathered the best of them.

Third dam Finder's Fee (Storm Cat) was a multiple Grade 1 winner who took the Grade 1 Matron S. and the Grade 1 Acorn S. Receipt was the only black-type performer among her five winners.

Finder's Fee is a daughter of the Grade 1 winner Fantastic Find (Mr. Prospector).

Feathered has a two-year-old full brother to Flightline named Olivier, a yearling colt by Curlin named Eagles Flight and a filly foal by Into Mischief, and has been covered by Tapit again.