The phone number of Allegiant Air Customer Service is 702-505-8888. Other customer service phone number with regards to baggage service office, lost and found service and TTY service are provided below. They are open 24/7. Allegiant Air also provides a Live Chat support that you can get help and assistance for all the issues. They are available from 6:00 am to 10:00 pm throughout the week (EST). Email support assistance is also available but it is best to call the customer service as email response usually take about a week or so. You can send them an email from Allegiant Air Contact Us page and send in your customer request for assistance. Particulars such as travelling with pets, travelling with children, baggage guide etc are all available in Allegiant Air FAQs section.