The behavior of a sound wave is affected by the density of the medium, the temperature of the medium and the pressure of the medium if it is a gas. Motion of the medium independent of the sound wave may also affect the way sound propagates.
Yes, you may check-in for your Delta Air Lines (DL) flight with your mobile device starting 24 hours and ending 60 minutes before the scheduled departure time (depending on your departure city and destination) to receive a mobile boarding pass on your mobile device.
When do I need to be at the departure gate? Check-in options. There are many ways to check in for your United- or United Express-operated flight, depending on where you are in your travel experience. At 24 hours before departure. Starting 24 hours before your scheduled departure time, you can check in for your flight in the following ways: 1  Go to united.com/checkin. Enter your confirmation or eTicket number and last name. 2  Open the United app, click the Check-in box and enter your confirmation or eTicket number and last name in the designated fields.