[saosebastiao]

For an aircraft that is not yet flying, the 777-9 has pretty healthy demand from multiple airlines. Lufthansa, Etihad, Qatar, All Nippon, and Singapore have all placed orders. Iran Airlines as well, although nullified by trade embargoes. The bigger 777-10x is also selling well.

[Xixi]

777-8 has 53 sales, and 777-9 has 273 sales, so a total of 326 firm orders. The 777-10 is not for sale, so it's certainly not selling well... 326 firm orders is pretty good, don't get me wrong, but the order book doesn't look super healthy: only 8 airlines, and 46% of the orders for Emirates. With Etihad troubled finances, that might go down to 7 airlines.

The order book has depth, but lack breadth. I've often heard the critical size for a widebody is at least 400 sales to 20 airlines. 400 sales to achieve economy of scales, and 20 airlines to have a healthy secondary market. The 777X is not far from the 400 sales, but has some ways to go to find 20 customers. The A330NEO is in a similar but reversed situation: 278 orders for 15 customers (including a couple of lessors). The breadth is nearly there, but not the depth.