the aviators began to come aboard irregularly : they were not an assembled crew , of course , with their own dragon , but rather were drifting over from dover covert , by twos and threes , including two of the captains jane had sent : both of them older men lately dropped to earth by the death of their former dragons , in the dreadful epidemic , long before anyone had looked for such an event ; experienced men , who might have looked for long careers ahead of them .