Of course, it is now possible to "hook up" or meet other solo travellers online and arrange for a rendezvous in Corfu or Casablanca. This is particularly popular for young backpackers travelling through Africa and India.
And, if you don't "do" mid-air/bus/train conversations and prefer to catch up on sleep, the films you have missed or some valuable reading time, it's easy enough (usually!) to send that signal out to the person in the next seat who seems to be settling in to show you family photos. You can put on your sleep mask and feign soft snores, pretend you have limited English or bury yourself in your book or in-flight entertainment.
One of the most uncomfortable flights I encountered was a long night flight when I was seated by a young Israeli off to surf in Bondi. He was very polite and incredibly attractive. I knew I couldn't possibly go to sleep and snore loudly beside such an impossibly handsome young man and so sat rigidly fighting sleep. I ruined it by succumbing to sleep just as we were about to land in Sydney and stunning the whole row awake with a thunderous snort.
But, it was an old Air New Zealand teal-coloured bag that caught my homesick eye in the crush of a Cairo street and led to a special friendship with a Kiwi traveller. I was desperate to hear those Kiwi vowels and tapped her on the shoulder, starting a long-lasting friendship.
She travelled extensively and when I went to Christchurch for her last farewell a few years ago, I wasn't surprised that her ashes were kept in a travel bag, among her souvenirs of exotic places.
I never get tired of watching that amazing theatre — the travelling public — and it's often just as interesting on the ferry to Stewart Island as it is on a flight to an exotic location.