Date: 201506
Local time of day: 1801-2400
Location: TEB.Tower, NJ
Flight conditions: VMC
Light: Daylight
Aircraft: Small Transport
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Flight phase: Climb
Airspace: Class B N90
ATC / advisory: TRACON N90
Reporter organization: Government
Reporter function: Ground
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: Pilot Not Flying; Captain
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: A flight called Ground Control for taxi. A similar aircraft [same company with the same first and last digit in three digit flight number] also had a flight progress strip for a VFR departure. On Ground Control; I issued instructions that would be relevant for a VFR departure and used the full call sign Flight 2. Flight 1 answered; read back the instructions; and used his call sign (Flight 1). Flight 1 continued to the runway; where he was switched to Local Control; who issued a VFR climbout instruction and cleared him for takeoff. Flight 1 (still answering to Flight 2's call sign; but reading back his own) departed; did not follow the instructions; and flew the Teterboro 9 Departure procedure. Departure Control was notified and no loss of separation occurred. The readback/hearback error occurred initially on my position (Ground Control) however at no point did Flight 1 make an attempt to correct the call sign. He also accepted a VFR departure clearance; then flew an IFR flight path without questioning the instructions. Pilots need to be more aware of the instructions they're issued and if they don't match their clearances; at the bare minimum question them before taking off.


Second narrative: For this flight; Captain was in left seat as non-flying pilot; First Officer was in right seat as flying pilot. The First Officer obtained the IFR clearance prior to taxi and the flight was cleared IFR via the TEB9 Departure. While ready to taxi; the Captain requested a taxi clearance for departure. ATC responded with the wrong call sign (Flight 2). I corrected them with my correct call sign (Flight 1) to ensure it was our clearance. The only other company flight at the airport had a completely different flight number. We were cleared to taxi via Golf Taxiway and told hold short of Runway 6 and follow a King Air. We proceeded. While taxiing we corrected Ground three times with our correct company call sign. Ground control kept referring to us as Flight 2; I kept correcting them. Ground then cleared us to taxi to Runway 1 for a Kilo Intersection departure. We thought this was unusual because we by-passed a lot of aircraft departing IFR; but didn't inquire because we assumed the sequence was out of order. We advised Tower that we were holding short of Kilo and readying for departure in sequence. Our takeoff clearance was 'Cleared for takeoff to the northeast.' Once again; this was unusual because we were IFR but I didn't inquire further because we had an aircraft approaching on short final. On departure; we flew the TEB9 SID as cleared but Tower asked us why we were turning to 280. After some discussion; they realized their mistake. They thought we were departing VFR even though we stated multiple times we were IFR and had an IFR clearance on file.The Tower was clearly training during a peak time of the day. You could hear multiple voices on the Tower frequency. It was high volume time of the day and it appeared we got lost in the shuffle. I could have inquired more while on with Tower before departure to figure out about her multiple mistakes.


Synopsis: Turboprop flight crew with an IFR clearance accepts taxi and takeoff instructions for a company VFR flight with a very similar call sign. The First Officer read back his call sign each time thinking the Controller was making an error and the controller ignored it each time thinking the pilot was making an error.