Date: 201911
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: clear; 50
Light: Daylight
Aircraft: Learjet 36
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Reporter organization: Corporate
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Communication Breakdown; Human-Machine Interface
Second reporter function: Pilot Flying; Captain
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Regained Aircraft Control; Flight Crew Returned To Clearance; Flight Crew Overcame Equipment Problem
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: While enroute to Maui HI from ZZZ. We were cleared to flight level 400. Prior to entering Oceanic airspace it became clear that we were not going to be able to make FL400. I requested to stop at FL380 but was told there was traffic 80 miles ahead at the same altitude; so I was told to climb to FL390. At approximately 38700 ft. the airplane became unstable and was very close to the stall speed. I took emergency action by turning off the airway and started a decent to FL380 at the same time advising ATC of my actions. I was about to [Request Priority Handling] when ATC told me to continue to FL 370. As soon as I started down the aircraft was stable and no other action was needed. I never got a chance to [Request Priority Handling] due to the Controller giving me the decent. The aircraft never entered a stall and due to my actions and the controllers the aircraft was in control the whole time.Was told to contact ATC which I did upon arriving in Maui and I explained my actions to the Controller. I used emergency authority to prevent the aircraft from stalling and endangering my passengers and other aircraft who could have been below me.


Second narrative: While enroute to Maui; HI we were cleared to FL400. We were unable to make 400 due to our weight and requested to stop our climb at FL380. This was denied and we were cleared to FL390. At 38700 ft. the aircraft was getting close to the stall speed and we advised ATC that we needed to return to FL380 for safety. We started down to prevent a stall and ATC cleared us to FL370. We turned off the airway and used emergency procedures before we started our decent. Once we were lower the plane was stable and no further action was required.We never got a chance to [Request Priority Handling] due to the quick actions of ATC.We were prepared to [Request Priority Handling] if we had to. The plane never stalled and we had complete control during the whole procedure. In the interest of safety we did what needed to be done using Captain's emergency authority. We were told to contact ATC upon landing which we did and explained our actions to the supervisor.


Synopsis: LR-36 flight crew reported a communications breakdown with ATC during an urgent altitude revision request.