Iryda for possessing longitudinally "heavy" controls, a relatively high approach speed, and the capability of its avionics. In February 1996, the Polish Air Force grounded its Iryda fleet and froze its orders for the type following a fatal accident on 24 January of that year. The accident, which was reportedly the result of a trim-related issue, and its investigation became highly politicised. During March 1996, the Warsaw Institute of Aeronautics abandoned development of its new D-18A engine, which was intended to power future combat-orientated versions of the Iryda, reportedly due to market viability concerns. In April 1996, the programme was officially resumed in response to a fresh order from the Polish Air Force, which involved the purchase of six new-build aircraft and the retrofitting of 11 existing aircraft in air force service with improved engines, avionics and wings by 1998. During October 1996, PZL-Mielec stated that it aimed for an upgraded prototype to be flown prior to the end of the year; the company also had ambitions to secure a follow-on order in the coming year, as well as for an modified maritime reconnaissance/strike version that were envisioned to replace the Polish Navy's fleet of MiG-21bis fighters. In June 1997, an Iryda flew for the first time with both the upgraded avionics package and the aerodynamic improvements. Full-scale flight testing of the upgraded aircraft was reportedly set to commence during August of that year; it was anticipated that the upgrade would be certified during 1998, after which the Polish Air Force would commence operational use of the type. Cancellation and relaunch efforts Relations between PZL-Mielec and the Polish Defense Ministry broke down in the second half of 1997, culminating in the company opting to sue the ministry over its alleged failure to honour the terms of a contract pertaining to the Iryda. While PZL-Mielec claimed that the Defense Ministry had demanded additional unfunded factory testing, the ministry accused the company of negligence, and claimed that the aircraft lacked necessary quality-control certification to be deemed safe for test flights. The prototype was grounded while legal action proceeded. The Polish Air Force's procurement of the Iryda was formally cancelled in 1998, allegedly in response to the development difficulties experienced as well as the protracted shortage of funding that was common around this period; a key event that had reportedly contributed to its cancellation was the fatal crash in 1996. In the summer