Hi

actually tv credits don't return first_airdate for crew.

cast field

{
  "character": "",
  "credit_id": "5256e69419c2956ff60e1ba4",
  "episode_count": 1,
  "first_air_date": "2004-09-22",
  "id": 1432,
  "name": "Veronica Mars",
  "original_name": "Veronica Mars",
  "poster_path": "/ewG884trMtmm8FrEAxOKVQDd8cD.jpg"
}

crew field

{
  "credit_id": "5256f0db19c2956ff611034d",
  "department": "Writing",
  "episode_count": 9,
  "id": 1437,
  "job": "Writer",
  "name": "Firefly ",
  "original_name": "Firefly",
  "poster_path": "/jFykyPcd92ecGJwwiqhssoS6MTO.jpg"
}

is There a reason to this ? Are you planning to change this ?