| Tail Number / N-Number | N521SL |
| Manufacturer | SCHLEICHER |
| Model | ASK-21 |
| Year Built | 2006 |
| Manufacturer's Serial Number | 21809 |
| Aircraft Type | Glider |
| Category | Land |
| Builder Certification | Type Certificated |
| Number of Seats | 2 seats |
| Weight Class | CLASS 1 (Up to 12,499 pounds gross take off weight) |
| Engine Manufacturer | NONE |
| Engine Model | NONE |
| Number of Engines | 0 engines |
| Type of Registrant | LLC |
| Owner Name | NFM ENTERPRISES LLC |
| Street | 50 BARONE RD |
| City | WURTSBORO |
| State | NY |
| Zip Code | 12790-5237 |
| Region | Eastern |
| County | Sullivan County |
| Country | US |
| Fractional Ownership | No |
| Airworthiness Classification | Standard |
| Airworthiness Date | 2006-03-30 |
| Certificate Issue Date | 2020-08-20 |
| Last Action Date | 2020-08-20 |
| Expiration Date | 2027-08-31 |
| Status | Valid Registration |
| Mode S Code | 51507100 |
| Mode S Code Hex | A68E40 |