- https://ifca-hof.org/wp-content/uploads/formidable/2/united-airlines-booking-assistance-for-beginners.pdf
- https://ifca-hof.org/wp-content/uploads/formidable/2/american-airlines-us-contact-numbers-official-guide.pdf
- https://ifca-hof.org/wp-content/uploads/formidable/2/Complete-guide-united-airlines-flight-booking.pdf
- https://ngspa.org/wp-content/uploads/formidable/22/american-airlines-usa-customer-service-contact-numbers.pdf
- https://ngspa.org/wp-content/uploads/formidable/22/Complete-List-of-Delta-Customer-USA-Contact-Numbers.pdf
- https://ifca-hof.org/wp-content/uploads/formidable/2/delta-airlines-phone-booking-assistance.pdf