| Tail Number / N-Number | N991MK |
| Manufacturer | KEYSTONE HELICOPTER CORP |
| Model | S-76C |
| Year Built | 2009 |
| Manufacturer's Serial Number | 760776 |
| Aircraft Type | Rotorcraft |
| Category | Land |
| Builder Certification | Type Certificated |
| Number of Seats | 19 seats |
| Weight Class | CLASS 1 (Up to 12,499 pounds gross take off weight) |
| Engine Manufacturer | TURBOMECA |
| Engine Model | ARRIEL 2S2 |
| Engine Type | Turbo-shaft |
| Number of Engines | 2 engines |
| Horsepower per Engine | 817 hp (609 kW) |
| Total Horsepower | 1,634 hp (1,219 kW) |
| Type of Registrant | LLC |
| Owner Name | MERCK SHARP & DOHME LLC |
| Street | C/O AVIATION SERVICES 100 SAM WEINROTH RD |
| City | WEST TRENTON |
| State | NJ |
| Zip Code | 08628 |
| Region | Eastern |
| County | Mercer County |
| Country | US |
| Fractional Ownership | No |
| Airworthiness Classification | Standard |
| Airworthiness Date | 2009-08-14 |
| Certificate Issue Date | 2022-06-02 |
| Last Action Date | 2022-06-02 |
| Expiration Date | 2029-06-30 |
| Status | Valid Registration |
| Mode S Code | 53353567 |
| Mode S Code Hex | ADD777 |