The irony off course is that the F35B (MARINES) is factually a 2-engined (2 propulsion sources) equipped fighter in the most crucial phase of its flight (TO and LANDING both rolling and vertical), ironic even more that it is an added liability iso an extra safety because any failure of one of both power-sources (which are mechanically coupled= extra risk) leads to an immediate catastrophic failure.
The YAK-41 suffered from this shortfall too btw.
Also the notion that 2 engines or more don't provide an extra safety measure is just plain and simple wrong (and I cannot understand why anybody would say differently).
the US DoD, at the end of the millennium, did a widespread statistical study on engine related class-A mishaps and did indeed show a significant elevated risk for single engined aircraft, the F16 being the best performer for single engined fighters was still far behind one of the weaker performing twins like the F14.
That being said, I do think that , under most circumstances, nowadays a single engined fighter, trainer or other single or twin-seater , is a very viable option because of improved technological fidelity.
EDIT,
found a younger chart from 2014 (not as detailed as study mentioned before)
http://www.afsec.af.mil/shared/media...140729-015.pdf
Also both the ISRAELI air force ,and before the USAF (during VIETNAM), found a strong correlation between risk for single engined fighters performing ground support tasks (close air support) and multi engined fighters.
The F104 was very susceptible to ground fire , the F5 and F4 much less so (props are also better btw).
Pierre Sprey's remark concerning the survivability of the F35 against light ground weapons was actually valid.