For Pilatus, the Porter was a commercial design first, but the Swiss armed forces became one of its most loyal users. German-language reference works give the Swiss Air Force fleet as 19 aircraft over the years, of which around 15 remained in military use, with one more operated by armasuisse, the federal procurement agency. The aircraft serve as light STOL transports and utility aircraft, a role that suits a country of short valley airfields.

Rather than replace them, Switzerland chose to update its Porters. From 2018 armasuisse delivered modernised aircraft with a glass cockpit and electronic map, new radios and GPS, new wiring, a civil transponder and a collision warning system, according to its own magazine. The approach mirrors the wider Turbo Porter fleet: in 2008 Pilatus began work on a Garmin glass cockpit retrofit after a French Air Force contract, and FlightGlobal estimated the upgrade at about $295,000 per aircraft. For MiGFlug readers who have watched a Porter climb out of an Alpine valley, the type is as Swiss as the PC-7 and the Hunter.

The Porter’s best-known wartime work was done by civilians. During the 1960s and 1970s Air America, the airline secretly owned by the CIA, flew up to 23 PC-6s at a time across Laos, Vietnam and Thailand. They dropped supplies to remote outposts, moved people, carried out reconnaissance and flew intelligence missions, landing on mountain strips that were often little more than a cleared ridge. Air America found the early Astazou-engined Turbo Porters unreliable and re-engined many with the Garrett TPE331.

The US Air Force tried to turn the Porter into a gunship. Fairchild built 15 AU-23A Peacemakers with a 20 mm side-firing cannon and underwing stores for the Credible Chase programme, intended to give the South Vietnamese Air Force a light armed aircraft. In the Pave Coin evaluation of June and July 1971, according to the National Museum of the US Air Force, American crews flew 73 missions and Vietnamese crews 68. The evaluating unit recommended against combat use without a major upgrade because the aircraft was slow and unarmoured. The Peacemakers were stored and then sent to Thailand, which used them for border surveillance and counter-infiltration work.

• PC-6 and PC-6/350 Porter: piston-engined originals with Lycoming engines.
• PC-6/A series: Turbo Porter with the Turbomeca Astazou turboprop, first flown in May 1961.
• PC-6/B series: Pratt & Whitney Canada PT6A turboprop from 1966, the standard version; the B2-H4 added a strengthened airframe and higher weights.
• PC-6/C series: Garrett TPE331 turboprop, including Fairchild-built aircraft.
• AU-23A Peacemaker: Fairchild-built armed version for the US Air Force, later transferred to Thailand.
• UV-20A Chiricahua: US Army designation for Porters flown by the Berlin Brigade.

The Porter is a single-engine turboprop with fixed undercarriage and simple systems, so its running costs are modest by military standards. Fuel for the PT6A-27 and the reserve for engine overhauls make up most of the direct cost, which is why civil operators in China saw it as cheaper to operate than the Antonov An-2, as AIN reported in 2016. The more serious cost is the lack of a direct successor: production ended in 2022, so air forces such as Switzerland and Austria have had to choose between upgrading old airframes, as Switzerland did from 2018, and buying a different type.

Different sources give different totals. One common count is 604 aircraft; another splits production into 521 built by Pilatus and 92 by Fairchild Hiller. Fairchild’s share is often rounded to about 100. Late in the programme some fuselages were built by a Pilatus joint venture in Chongqing, China. The figure of about 600 is used here as a rounded total.