| Tail Number / N-Number | N21723 |
| Manufacturer | BOEING |
| Model | 737-724 |
| Year Built | 1999 |
| Manufacturer's Serial Number | 28790 |
| Aircraft Type | Fixed wing multi engine |
| Category | Land |
| Builder Certification | Type Certificated |
| Number of Seats | 149 seats |
| Weight Class | CLASS 3 (20,000+ pounds gross take off weight) |
| Engine Manufacturer | CFM INTL. |
| Engine Model | CFM56 SERIES |
| Engine Type | Turbo-fan |
| Number of Engines | 2 engines |
| Horsepower per Engine | 2,200 hp (1,641 kW) |
| Total Horsepower | 4,400 hp (3,282 kW) |
| Type of Registrant | Corporation |
| Owner Name | UNITED AIRLINES INC |
| Street | ATTN: TREASURER - WILLIS TOWER 233 S WACKER DR |
| City | CHICAGO |
| State | IL |
| Zip Code | 60606-7147 |
| Region | Great Lakes |
| County | Cook County |
| Country | US |
| Fractional Ownership | No |
| Airworthiness Classification | Standard |
| Airworthiness Date | 1999-04-21 |
| Certificate Issue Date | 1999-04-23 |
| Last Action Date | 2022-09-09 |
| Expiration Date | 2030-01-31 |
| Status | Valid Registration |
| Mode S Code | 50353075 |
| Mode S Code Hex | A1D63D |
Deregistered Aircraft 1 of 2. This aircraft was previously assigned the N-number N21723.
| Tail Number / N-Number | N21723 |
| Manufacturer | PIPER |
| Model | PA-31-350 |
| Manufacturer's Serial Number | 318152028 |
| Aircraft Type | Fixed wing multi engine |
| Category | Land |
| Builder Certification | Type Certificated |
| Number of Seats | 8 seats |
| Weight Class | CLASS 1 (Up to 12,499 pounds gross take off weight) |
| Number of Engines | 2 engines |
| Average Cruising Speed | 162 miles per hour |
| Type of Registrant | Corporation |
| Owner Name | SPECIAL AIR SERVICE CORP |
| Street | 10661 N KENDALL DR STE 101 |
| City | MIAMI |
| State | FL |
| Zip Code | 33176 |
| County | Cook County |
| Country | US |
| Certificate Issue Date | 1994-08-02 |
| Last Action Date | 1994-08-03 |
| Last Status | Valid Registration |
| Cancellation Date | 1994-12-02 |
| Exported To | CHILE |
Deregistered Aircraft 2 of 2. This aircraft was previously assigned the N-number N21723.
| Tail Number / N-Number | N21723 |
| Manufacturer | HEIDEMAN-BOWLUS |
| Model | B-3 |
| Year Built | 1940 |
| Manufacturer's Serial Number | 3 |
| Aircraft Type | Glider |
| Category | Land |
| Builder Certification | Not Type Certificated |
| Number of Seats | 2 seats |
| Weight Class | CLASS 1 (Up to 12,499 pounds gross take off weight) |
| Number of Engines | 0 engines |
| Type of Registrant | Individual |
| Owner Name | TORGERSON RUSSELL EUGENE |
| Street | 1350 TETON DR |
| City | EL CAJON |
| State | CA |
| Zip Code | 92021 |
| Region | Western-Pacific |
| County | Cook County |
| Country | US |
| Certificate Issue Date | 1958-12-16 |
| Last Status | Valid Registration |
| Cancellation Date | 1967-06-29 |