In fact, it does not isolate much as compared to other IEMs, and probably not an ideal IEM for flight if you are looking for one to block noise.
It is also designed with the most of IEM located outside the ear when wearing it, thus you get wind noise when walking.
The sound is good, only when listen in quiet moments, which is not as useful.
I use it at home during quiet time, but have my SE846 for everything else and best fit for flight. Sound is comparable, but with most of the situation, my SE846 sounds better than my Z5.
Isolation and comfort is critical for an IEM, so test out before buying.