Hanuman could fly, there are numerous descriptions of people with a lot of rare Siddhis. In the book Autobiography of A Yogi, there are accounts of people who could levitate, summon materials from ethereal realms, can exist at multiples places at once etc.
How much importance should be given to these Siddhis according to Hindu scriptures?
Yoga Vashishtha, is a conversation between Shri Rama and Maharishi Vashishtha. Shri Rama asks a similar question to which Maharishi Vashishtha responds.
Rama asked:
Lord, why do we not see many of these liberated sages traversing the sky now?
Vashishtha replied:
Flying in the sky and other powers are natural to some beings, O Rama. The extraordinary powers and faculties which are observed in this world are natural to those beings - not to sages of self-knowledge. Supernatural faculties (like flying in the air) are developed by even those who are devoid of self-knowledge or liberation, by the utilisation of certain substances or by certain practices. All this does not interest the man of self-knowledge who is utterly content in himself. They who, in pursuit of pleasures, acquire these powers tainted by ignorance, are surely full of ignorance; the sages of self-knowledge do not adopt such a course.
Whether one is a knower of truth or ignorant of it, powers like flying in the air accrue to one who engages himself in some practices. But the sage of self-knowledge has no desire to acquire these. These practices bestow their fruit on anyone, for such is their nature. Poison kills all, wine intoxicates all, even so these practices bring about the ability to fly etc., but they who have attained the supreme self-knowledge are not interested in these, O Rama. They are gained only by those who are full of desires; but the sage is free from the least desire for anything. Self-knowledge is the greatest gain; how does the sage of self-knowledge entertain any desire for anything else?
Reference used: http://www.estudantedavedanta.net/The-Supreme-Yoga-Swami-Venkatesananda.pdf