Our favorite bike cases combine protection and convenience; these include the EVOC Pro, Thule RoundTrip Traveler and Biknd Helium V4.
They use rigid bases that cradle your frame while padded wheel pockets provide cushioned protection during transport.
Hard cases provide the highest level of protection, yet can often be heavier and subject to oversize luggage fees.
Soft cases tend to be lighter and more maneuverable while still offering some degree of protection; they're just not quite as strong.