Let’s look to history 101 for a moment. And some simple Newtonian mechanics. Pull up a chair.

It was said back then in the 1950’s, sure, that the twin brought with it an additional sense of assurance. And in fact that might be why our rebbe concured. But as pointed out by analysts, turning to supposedly safer actually resulted in more disappointing statistics.

The reason it turned out that way was because with that second engine came a need for additional skill. In a twin, a flameout now required coordination of all 4 extremities. The compromised craft needs be balanced skillfully against torque resulting from the asymmetric forward thrust (picture the strain in Dvarim 22:10 לֹא תַחֲרֹשׁ בְּשׁוֹר וּבַחֲמֹר יַחְדָּו). Parallel forces necessitate skill to keep the bowling ball in line.

But skills rust with time. So the additional assurance benefited just those who’d put in the effort to keep their skills current. Such as within the rigorous training of the USAF. Those in the general aviation sector, however, or private owners, had mostly not demonstrated the self-motivation to invest in the ongoing training needed for handling disruption in a twin. Thus its reputation of a weaker safety profile.

This led to the return of the single engine camp, especially as engines were becoming increasingly more reliable. Which is why today authorities recommend the average buyer go with the single.

So it okay to fly single

Not understanding what you wrote about 4 engines etc

Planes have possibly evolved, but unfortunately such tragedies happen once in a while. There was another such crash a few years back also with 2 frum yidden (iirc reported by anash.org as well). There’s no reason to believe that the Rebbes holy instruction is no longer in effect imho

Umm source
You see some letters when your average plane has 4 engines when now almost none have. Planes evolved majorly since the 50’s

A helicopter also only has one engine