It hasn't been a 1-for-1 replacement. At least for BA the 747 has been replaced by the A380, 777, and 787 on many routes. All 3 have different capacities to sca

It hasn't been a 1-for-1 replacement. At least for BA the 747 has been replaced by the A380, 777, and 787 on many routes. All 3 have different capacities to scale with demand; 787 < 777 < A380. And all 3 are more fuel efficient per passenger than the 747.