The 777 accounts for 5% of the CAL fleet which means you have to be in the top 5% of all captains to make a 777 captain. Well, maybe it is slightly easier as some of the top captains may prefer a better base and the 767 than the 777 and Newark for example, but the point is it is a very small percentage.

In this respect UAL is the best – 18% of their planes are 777s and 747s. That's a lot easier to get to.

Looking at all wide-bodies – they account for 12%, 22%, 24% and 26% of the total fleet for CAL, AMR, DAL and UAL, respectively. So you need to be in the top 12% of all CAL captains to fly a wide-body, while at the others you just need to be in the top quarter of all captains. I picked three random airlines that are similar in size to CAL for the purposes of this comparison.