Fixed

gistfile1.vb

Dim PassengerData As String

If strSSN.Length = 11 Then
  PassengerData = strSSN + " "
Else
  MessageBox.Show("Please enter a valid SSN")
  Return
End If

If strFirstName.Length <= 30 Then
  PassengerData += strFirstName + " "
Else
  MessageBox.Show("First name may only contain up to 30 characters")
  Return
End If

If strLastName.Length <= 30
  PassengerData += strLastName + " "
Else
  MessageBox.Show("Last name many only contain up to 30 characters")
  Return
End If

If strPhoneNumber.Length = 12 Then
  PassengerData += strPhoneNumber
Else
  MessageBox.Show("Please enter a valid phone number")
  Return
End If

PassengerDataList.Items.Add(PassengerData)