Is it permissible for a traveler on an airplane, who suffers from the discharge of a viscous substance that necessitates repeating ablution, to perform ablution before the time for Fajr prayer begins? And is it permissible to pray sitting down on the airplane, and is it obligatory to repeat the prayer after arriving?

If this discharge is from vaginal secretions and is continuous, it is considered سلس (urinary incontinence or perpetual discharge), which invalidates ablution (wudu') but is pure. It is obligatory for the person experiencing this سلس to renew their ablution after the entry of every prayer time. However, if it stops for a sufficient time, one must wait for it to stop before performing ablution and prayer. If it is not from vaginal secretions, then it is impure (najis) and invalidates ablution.

To perform prayer on an airplane, perform ablution if possible. Otherwise, perform tayammum (dry ablution). If neither is possible, perform the prayer without them, but repeat the prayer when water or pure earth (الصعيد) becomes available. It is permissible to adopt the Maliki school of thought, which holds that سلس (perpetual discharge) does not invalidate ablution. Prayer on an airplane must be performed to the best of one's ability: standing if possible, otherwise by gesturing while seated, facing the Qiblah and turning with it if the airplane changes direction.