On Sunday 15 June 2025, thousands of people packed the beaches of the Mar Menor in Murcia to watch seven red-and-yellow jets trail the colours of the Spanish flag one last time. King Felipe VI was among them. The Patrulla Águila was flying its final display, and with it Spain was saying goodbye to the aircraft that had trained almost every one of its military pilots for 45 years.

That aircraft was the CASA C-101 Aviojet. It was never glamorous. Its wings were straight, its engine came from a business jet, and Spanish pilots nicknamed it “Culopollo”, chicken’s backside, because of its high tail. But it was Spain’s own, and few trainers have been loved quite like it.

Spain designs its own jet

In 1975 the Spanish Air Force wanted a replacement for its ageing Hispano HA-200 Saeta trainers. Construcciones Aeronáuticas SA, better known as CASA, won the contract. It had built aircraft for half a century, but mostly other people’s designs under licence, so it brought in help: Messerschmitt-Bölkow-Blohm of West Germany worked on the rear fuselage and tail, and Northrop of the United States on the wings and engine intakes.

The result was deliberately simple. Where the BAE Hawk et Alpha Jet had swept wings, the C-101 had straight ones. Its engine was a Garrett (now Honeywell) TFE731 turbofan, a design developed for business jets, chosen for its fuel economy. The two crew sat in tandem, with the instructor’s rear seat raised for a better view.

There were some clever touches. A bay under the cockpit could carry weapons or equipment, giving the trainer a light attack and reconnaissance role. The landing gear was reinforced to survive student landings, and the tail was set high so that it would not strike the runway if a nervous pilot flared too steeply. That tail gave the jet its affectionate nickname.

The first prototype flew in the summer of 1977; most sources give 27 June. The aircraft entered Spanish Air Force service on 17 March 1980 under the designation E.25 Mirlo, or Blackbird, and Spain eventually took 88 of them. In total, Airbus says, 151 C-101s were built at Getafe near Madrid, including four prototypes.

Forty years of the Patrulla Águila

On 4 June 1985, five instructors from the Air Force Academy at San Javier flew the first training sortie of a new aerobatic team. The Patrulla Águila, or Eagle Patrol, inherited the tradition of the Patrulla Ascua, which had flown F-86 Sabres in the 1950s. It soon grew to seven C-101s.

Over four decades the team flew more than 500 displays, over 170 of them outside Spain, and became famous for painting the red and yellow of the Spanish flag across the sky with coloured smoke. Its pilots were instructors at the academy, so the jets that flew at international airshows were the same type cadets learned on during the week.

The Patrulla Águila’s seven C-101s displaying at Airpower 2024 in Austria, one of the team’s last seasons.

The C-101 had less thrust than the jets of other European teams, and the pilots had to fly around that. Lieutenant Óscar Sanz, one of the last Patrulla Águila pilots, told Airbus that it made up for it in other ways.

Export trainers and light attack jets

CASA followed the trainer with armed versions. The C-101BB had an uprated engine and could carry weapons, and the C-101CC of 1983 was a dedicated light attack version with more power and more fuel. These variants found three export customers.

The biggest was the Chilean Air Force, which operated 35 C-101s, many of them assembled locally by ENAER in partnership with CASA. Chile used them for 39 years to train its combat pilots. According to the Chilean Air Force, its jets flew more than 40,000 hours and trained more than 260 F-5 et F-16 pilots before they were retired in December 2022 and replaced by the Embraer A-29B Super Tucano.

Le Royal Jordanian Air Force bought the attack-optimised C-101CC, and the Honduran Air Force took a small batch of C-101BBs. In Spain itself, the E.25 carried on as the backbone of military pilot training into the 2020s.

Defensa y Aviación’s farewell to the C-101 Aviojet (in Spanish).

A turboprop takes over

By then the C-101 was running out of airframe life. In January 2020 Spain signed a contract worth more than 200 million euros for 24 Pilatus PC-21s, a single-engine turboprop that Pilatus said would replace the C-101s in use since 1980. The PC-21 took over basic training at the academy in 2022, and regular C-101 training flights ended that year.

The Patrulla Águila kept flying its Aviojets until the 40th anniversary display at the Aire25 festival at San Javier in June 2025. By then the C-101 fleet had logged some 285,000 training flight hours. At the same festival, King Felipe VI went up in a PC-21, the type his daughter, Princess Leonor, would train on.

At first the plan was for the team to re-equip with PC-21s. Instead, the air force created a new five-ship PC-21 formation, the Formación Mirlo, which made its debut over Madrid on Spain’s National Day, 12 October 2025. Reports at the time said it flew formation flypasts rather than a full aerobatic display.

What comes next

For advanced jet training, Spain has chosen the Turkish Hürjet, known in Spain as the Saeta II, with Airbus leading Spanish industry on local assembly and systems. According to El Español, the first of 21 aircraft are due from 2028. In April 2026 Airbus told the newspaper that it and the air force were studying whether the Saeta II could bring the Patrulla Águila back.

Spanish regional broadcaster La 7 on the Patrulla Águila’s farewell at San Javier in June 2025 (in Spanish).

If it does, the Eagle Patrol will return in a supersonic jet whose Spanish name recalls the very trainer the C-101 replaced in 1980. For now, the Culopollo belongs to museums and memories, and to the generation of Spanish pilots who learned to fly in its front seat.

Sources: Airbus (Aire25 and the legacy of the C-101, June 2025), Pilatus Aircraft, Air Data News, El Español, El Independiente, RTVC/EFE, Voz Pópuli, This Is Flight, Afterburner.com.pl

Header photo: Airwolfhound / Wikimedia Commons, CC BY-SA 2.0