Spoken Language Systems
MIT Computer Science and Artificial Intelligence Laboratory


What is Pegasus?
What does Pegasus know?
How do I talk to Pegasus?
How do I call Pegasus?
How does Pegasus work?

What is Pegasus?
A conversational interface that provides information about flight status, Pegasus enables users to obtain flight status information over a telephone line. Pegasus can provide information about flights within the United States, and can answer questions about departure and arrival time for flights that have taken off, landed, or filed a flight plan on the day the user queries the system. The knowledge Pegasus uses for answering queries about flight status is updated continually throughout the day by one of the leading providers of flight status information, RLM Software, Inc.

What does Pegasus know?
Pegasus has access to data from RLM, which contains information about the estimated departure and arrival times for flights that are either in the air or have filed a flight plan. In addition, Pegasus maintains information about actual arrival time for flights that have landed at any point during the current calendar day.

Because users do not always know the airline and flight number for a flight they are meeting, Pegasus also has information on flight schedules. This enables the user to ask about flights between two cities arriving around a particular time. Once the user narrows the search to one flight, the system can then consult the real-time status database to provide up-to-date arrival information.

How do I talk to Pegasus?
When talking with Pegasus, users must pay special attention to speaking style, noise, and correcting mistakes. Please consult the JUPITER homepage for further information.

Pegasus converses with the user until sufficient information is available to construct a complete schedule or status query. Here are some example dialogues with the system:


Pegasus: United flight 9 from Kennedy is expected in Los Angeles at 11:43 a.m. local time. It is 47 minutes minutes ahead of schedule. What else would you like to know?


Pegasus: There are 2 flights from Chicago arriving in Boston at 12 o'clock pm local time, United flight 506 scheduled to arrive at 11:53 a.m. and American flight 744 scheduled to arrive at 11:59 a.m. Please select one.


Pegasus: American flight 744 from O'Hare landed in Boston at 11:42 a.m. local time, 17 minutes minutes ahead of schedule. Is there something else you'd like to know?

How do I call Pegasus?

Here are some basic instructions:

  1. When you call, you will be connected with Pegasus (the connection will take about 5 sec.), and the system will greet you with something like "Welcome to Pegasus - the MIT Lab for Computer Science flight arrival and departure information service. How may I help you?"
  2. At this point, you will hear a brief high pitch beep, indicating that the computer is listening. You can now ask your question, e.g., what's the status of Continental flight twenty two, can you tell me about flights from Atlanta to Miami, etc.
  3. When you are done asking the question, you will hear a brief low pitch beep, indicating that the machine has detected an endpoint. It will entertain you with music and then respond (hopefully with the right answer!). If it doesn't do well, you may want to change your speaking rate a bit, or try not to trail off at the end of a sentence. You might also want to simplify your query, if you are having trouble with longer queries. The system does not do as well if you are in a noisy environment or if you use cell phones.
  4. When Pegasus is done, it will say "can I help you with something else" and go to step 2 again. When you are done, simply hang up.
  5. If Pegasus doesn't answer the phone, it's because someone else is using it. Wait a couple of minutes and try again. Also, remember that you are being recorded. We are using your voice and queries to improve the system!
  6. Please keep in mind that this is not a product, it is a research prototype. We are putting it out there primarily for the purpose of data collection. But it tends to do okay on reasonable queries.

How does Pegasus work?
During a call, Pegasus utilizes a set of core speech technologies developed by the SLS group the recognize, understand, and respond to each request from the user. To find requested flight information, Pegasus has access to flight status information that is updated continually throughout the day by RLM Software, Inc. With carefully planned dialogue management, Pegasus can help a user find the flight status of a particular flight, even if the user has forgotten the flight number.

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