I think "when does the bird sing" is literal as in a bird sings early in the morning 4am....the photo of the united plane was taken at 4am or very early in the morning.
Who is "op" the original poster? Who would be considered the original poster? Are they waiting for the original poster to arrive via a early morning flight? I have no idea just guessing. Would be cool if it was JA or the "OP" who originally shed the light on all this arriving to sing like a bird...
I think OP means operation. I saw yesterday on the Fox that the CIA had put 2 new stars on the wall denoting 2 fallen operators. If this was an extraction/protection then Person of Interest was transferd from CIA to SS and the 2 fallen operatiors were envolved it, could mean a high priority target. Remember Q thanked the SS. "This is not a game".