Captain reported preparing for takeoff on runway 30 at opf was alerted by his copilot that an aircra...

Narrative:

Approximately XA55 this morning; my first officer (first officer) and I started taxiing at kopf for a XC00 departure from there. I arrived at the aircraft second (first officer had already obtained clearance and had accomplished all checklists prior to engine start). I closed cabin door and sat in the left seat; fastened seat belts; adjusted seat; and put headset on. An intercom check revealed that the headphone volume control had been turned down beyond where anything could be heard from my headset; so I adjusted it for normal intercom operation. When engine start had been completed; we accomplished before taxi checks and agreed we were ready for taxi. As we reached the hold-short line of runway 30; we stopped and contacted miami approach. Our original attempt on radio #2 was unsuccessful; so radio #1 was used to contact approach. I stated we were taxiing into position and waiting on runway 30. The first officer had understood this to mean we were not cleared for departure; and he announced on the CTAF (134.675) that we were lining up and waiting on runway 30. He did this on radio #2. When I realized he believed we were not cleared for departure; I told him we were cleared for departure; and he announced our departure on the CTAF. As I started to advance throttles for takeoff; he stated 'those lights look like a plane departing 12; we better get off the runway'. I complied and started to taxi to the right side of the runway. Within a few seconds; aircraft Y departed over us; on the runway. This 'excitement' caused us to miss our departure window; and we were again cleared for departure; read back our departure clearance; and took off on runway 30. As we were climbing out; we received a TA from the TCAS for aircraft Y; and it appeared to be the same [aircraft;] aircraft Y which had just taken off over our aircraft. When we adjusted our flight path to avoid aircraft Y; we were cleared to 6000' and had no more contact with the aircraft Y.when I queried ATC after landing; the supervisor advised us aircraft Y had departed without a flight plan; and was not participating in radar advisories; and was squawking 1200.

Original NASA ASRS Text

Title: Captain reported preparing for takeoff on runway 30 at OPF was alerted by his Copilot that an aircraft was departing runway 12; Captain taxied to the side of runway as the aircraft departed over them.

Narrative: Approximately XA55 this morning; my First Officer (FO) and I started taxiing at KOPF for a XC00 departure from there. I arrived at the aircraft second (FO had already obtained clearance and had accomplished all checklists prior to Engine Start). I closed cabin door and sat in the left seat; fastened seat belts; adjusted seat; and put headset on. An intercom check revealed that the headphone volume control had been turned down beyond where anything could be heard from my headset; so I adjusted it for normal intercom operation. When engine start had been completed; we accomplished Before Taxi checks and agreed we were ready for Taxi. As we reached the hold-short line of runway 30; we stopped and contacted Miami Approach. Our original attempt on radio #2 was unsuccessful; so radio #1 was used to contact Approach. I stated we were taxiing into position and waiting on Runway 30. The FO had understood this to mean we were not cleared for departure; and he announced on the CTAF (134.675) that we were lining up and waiting on Runway 30. He did this on radio #2. When I realized he believed we were not cleared for departure; I told him we were cleared for departure; and he announced our departure on the CTAF. As I started to advance throttles for takeoff; he stated 'those lights look like a plane departing 12; we better get off the runway'. I complied and started to taxi to the right side of the runway. Within a few seconds; Aircraft Y departed over us; on the runway. This 'excitement' caused us to miss our departure window; and we were again cleared for departure; read back our departure clearance; and took off on runway 30. As we were climbing out; we received a TA from the TCAS for Aircraft Y; and it appeared to be the same [aircraft;] Aircraft Y which had just taken off over our aircraft. When we adjusted our flight path to avoid Aircraft Y; we were cleared to 6000' and had no more contact with the Aircraft Y.When I queried ATC after landing; the supervisor advised us Aircraft Y had departed without a flight plan; and was not participating in Radar Advisories; and was squawking 1200.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1410588
Time
Date	201612
Local Time Of Day	0601-1200
Place
Locale Reference	OPF.Airport
State Reference	FL
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	Medium Transport High Wing 2 Turboprop Eng
Operating Under FAR Part	Part 91
Flight Phase	Taxi
Route In Use	None
Flight Plan	IFR
Aircraft 2
Make Model Name	Light Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Flight Plan	None
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 75 Flight Crew Total 11182 Flight Crew Type 1742
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 2693 Flight Crew Type 200
Events
Anomaly	Conflict Ground Conflict Critical Conflict Airborne Conflict Deviation - Procedural Published Material / Policy
Miss Distance	Vertical 300

Captain reported preparing for takeoff on runway 30 at opf was alerted by his copilot that an aircraft was departing runway 12; captain taxied to the side of runway as the aircraft departed over them.