kotakota,
That is mischievous. The 737 type certificate is perfectly adequate and an expression of the great quality of engineering in 1964 when it was designed. Just because the -100 was a little underweight at 42 tonnes does not lessen the quality of the design, and a modest stretch for later models to anything up to 100 tonnes or 10,000km range would seem quite reasonable. The engineering parameters of the later and larger models are exactly the same as the original. They all have windows at the front and sides, wings on both sides, two engines, and the tail is at the back. Clearly there is no need for re-certification yet, and any suggestion otherwise is unfounded.