-The disadvantages of e-tickets are relatively few; however, if you are less technologically savvy or don't use computers and email, you may find the online ticket purchasing system confusing. 
-You may accidentally delete the email containing your e-ticket or it may get lost among the many messages flooding your inbox. 
-E-tickets also take away some of the personalization of gifting a plane ticket to a friend or loved one.
1 1 1
1.A computer crash could cause a passenger's reservation and other information to simply vanish. 
2.everyone person solely depends on the computer and if there is virus in it then the information is gone
3.a person who does not knows to operate computer cannot use E-ticketing
4.some fake sites can simply withdraw the money from your account if our information and pin code is known to them while restring  for the seat