Efficient engines. 

Thrust to weight 7.5 
[[https://en.wikipedia.org/wiki/Shenyang_WS-10|Shenyang WS-10]]


Thrust to weight 3 - 5  
[[https://en.wikipedia.org/wiki/CFM_International_CFM56|CFM International CFM56]]

[[https://en.wikipedia.org/wiki/Xi'an_Y-20|Xi'an Y-20]]

[[https://defence.pk/pdf/threads/engines-used-in-different-fighters.118218/|Engines used in different fighters]]