The correct answer is 1 only.

Explanation:

1. Carbon fibres are used in the manufacture of components used in automobiles and aircrafts:
   • Correct: Carbon fibres are widely used in industries such as aerospace, automotive, and sports equipment manufacturing due to their high strength-to-weight ratio, durability, and resistance to corrosion.
2. Carbon fibres once used cannot be recycled:
   • Incorrect: Carbon fibres can be recycled, although the process is complex and expensive. Advanced technologies like pyrolysis and chemical recycling are used to recover carbon fibres from composite materials. The recycled fibres are often used in applications where slightly lower strength is acceptable.

Thus, only the first statement is correct.