Cathay Pacific

You can buy it a seat on this airline.

Cathay Pacific rules

Small instruments such as flutes or violins can be carried on in a hard case that fits the overhead compartment.
The cabin limit is 93 × 39 × 24 cm and 7 kg including the case, in every class.
Larger instruments such as cellos can travel on a purchased seat: up to 136 × 48 × 44 cm and 32 kg. Staff fasten it in.
Book the seat through customer care at least three working days before travel.
Otherwise the instrument is checked under normal baggage rules. Loosen the strings.

Cathay Pacific instrument policy

Small instruments in a hard case up to 93 × 39 × 24 cm and 7 kg are accepted as cabin baggage.

https://cathaypacific.com/cx/en_PH/baggage/musical-instruments.html