Amid growing tensions between Turkey and the Untied States over a number of critical issues, conflicting interests in the Syrian theatre and Turkish defence cooperation with and acquisition of advanced arms from Russia being key among them, lawmakers in Washington have with the support of a number of influential lobbyists groups pushed for the blocking of sales of the F-35 light stealth fighter to Ankara. Support for the sale's cancellation have gained growing momentum, with 44 member of the U.S. House of Representatives signing a joint letter calling for such action on June 15th. Turkey’s planned acquisition of the Russian S-400 surface to air missile system over Western made alternatives in particular has led to a number of key figures in the United States leadership to call for reprisals against the country for stepping out of line with the West’s pressure campaign against Russia, with the U.S. even threatening economic sanctions against the country under the Countering America’s Adversaries Through Sanctions Act (CAATSA), which was signed into effect in August 2017 and imposed penalties on states which made large purchases of Russian weapons. The threat of cancelling F-35 deliveries remains a secondary means for the United States to press Turkey to abandon its plans to acquire the S-400 and fall into line with other NATO members.
Further complicating Turkey’s planned acquisition of the F-35 light fighters to modernise its air fleet, Israel has raised concerns with the United States that should Ankara acquire the stealth fighter it would negate the Israeli Air Force’s advantage in a potential conflict between the two powers in the Middle East. Israel has thus requested that the United States, should it proceed with sales of the fighters, should deny the Turkish military the latest software for the stealth fighters - thus ensuring a continued Israeli advantage while providing Turkey with a downgraded variant of the F-35.
A number of Turkish sources have indicated that as a result of threats by the U.S. to cancel the sale of the F-35, Ankara could acquire the Russian Su-57 fifth generation air superiority fighter in its stead. By cancelling the F-35, not only would the United States lose one of its oldest clients for combat aircraft, but Israel, Greece and other potential Turkish adversaries would also find themselves facing a considerably more dangerous Turkish air fleet than they would have had Ankara purchased the American stealth fighter. While the Su-57 and the F-35 are both fifth generation fighters, the two are hardly comparable in their role or their capabilities. The F-35 designed as a lighter and less costly complement to the elite F-22 Raptor air superiority fighter, a platform no longer in production and banned from export, and itself lacks the specialisation of heavier fighters and retains poor air to air combat capabilities. The Su-57 by contrast was designed as a heavy twin engine air superiority platform, much like the F-22, and was intended to contend with American Raptors over Europe and the Pacific. Much like the F-22 Raptor is considerably more capable in an air to air combat role than the F-35, with the latter maintaining only limited defensive air to air combat capabilities, the Su-57 too retains a considerable advantage over the F-35 in the air. This is reflected in its speed, altitude, sensors, missile carriage, engagement range, and manoeuvrability - all fields in which the heavier Russian fighter is far superiority.
Turkey’s Air Force today fields a sizeable light fighter fleet, comprised of approximately 250 F-16 and 40 F-5 multirole platforms. The country’s air superiority capabilities however leave much to be desired, with the Vietnam War Era third generation F-4E Phantom remaining the country’s fastest, highest flying and most heavily armed platform and its only heavy fighter. While the F-35 would provide a considerably more modern light fighter for the Turkish fleet, it is arguably the country’s air superiority capabilities which are most in need of improvement - hence why the Su-57 could be the ideal platform for Turkey. While a fourth generation air superiority platform such as the F-15C or Su-30 would be sufficient to considerably enhance Turkish air superiority capabilities, a more advanced fifth generation heavy platform would provide the country with the most capable air superiority fighter in the Middle East or Europe. The Su-57 can also be equipped to function as a high end strike fighter - deploying advanced munitions such as the Drel fire and forget glide bomb, the Kh-59MK2 cruise missile as well as the highly sophisticated Kh-58 and Kh-38M. Many of these missiles are capable of travelling at several times the speed of sound, and are significantly more capable than the subsonic air to ground munitions relied on by the F-35 - a platform which relies heavily on low speed subsonic missiles. The heavy fighter's strike capabilities, coupled with its high survivability, could make it a highly value asset for operating in the Middle Eastern theatre. Should the U.S. proceed to terminate sales of the F-35 to Turkey, not only would Ankara move to rely more closely on Moscow for its defence, but the Turkish Air Force would also field a considerably heavier more capable and aircraft for its fleet. Acquisition of the Su-57 could also pave the way for Russian involvement in Turkey's indigenous fifth generation fighter project - thus effectively backfiring and severely undermining American interests.