That is one aspect that the missile-deniers are ignoring. The contrail is thick and opaque its entire length. Also, while it is true that a jet contrail often continues to widen to a point as it ages (until it dissipates into nearly invisible haze) it will appear to get narrower towards the horizon as it is many miles further away.
>>The contrail is thick and opaque its entire length. <<
No. It only APPEARS thick and opaque. And that is very common, especially when the clouds are still in sunlight but most everything else is not.