No redness or swelling, there is intermittent pain but only mild more of a throbbing sensation but I had it shortly after I got off the plane and mosst of the day.

No other disease, do not take medication

From what I have read it is sometimes the case that there are no symptoms with DVT's. My concern is that as this spasm/mild pain started directly after the flight and has, in my opinion, lasted a significiant amount of time - and not consistent with a pulled muscle - i.e. I can feel it when the muscle is totally relaxed. If the symptoms go away can I assume it is very unlikely to be a clot.

What I am unsure about is that if there are no further symptoms have the symptoms just gone away or they were as you suggest, just spasms

Typically, if DVT symptoms start in the first place, do they will continue?

Thanks