Puppy jumping at people on walks

We have a male, neutered, 16 month old, mix breed, medium sized puppy (dunno when I can’t call him a puppy anymore…)

He’s generally great, good recall, friendly, and we don’t have any major worrying behavioural issues.

This morning, we were out on a walk and he was off lead on a footpath. A woman came running from behind and I think she gave him a bit of a fright, he instantly was repeatedly jumping up at her. No signs of aggression or anything just really excited. The woman was not impressed and told us that “sorry wasn’t good enough”…

We’ve had a few similar issues in the past, he’s never aggressive only excited to see people but it’s obviously a behaviour we really don’t want. When he starts it’s like he gets super excited and is just repeatedly jumping and won’t stop until you grab him, especially when people start pushing him off – that just gets him more excited!

I worry that he will do it to someone who is unstable on their feet and cause them to fall and hurt themselves. He’s done it before to a man who had a baby strapped to his chest, ran from about 15m away to get to him.

We’re finding it hard to train because at home he would never jump up at us as he knows that we won’t allow it.

Any tips for training him out of this? he only does it with strangers when out so we’re finding it hard to train, can’t exactly find a stranger and say “will you run along so my dog can jump at you?”

Any tips/ tricks/ advice welcomed