Narrative:

Had incorrect barometer (30.27 vs 29.55) setting which resulted in leveling off approximately 700 [ft] below assigned altitude of 13;000 ft while descending into chicago airspace. Received a message from dispatch prior to descend stating 'attn crews: ATIS is reporting old info. Please check with dispatch for updated WX. The WX request page is still accurate.' we read the message but did not realize this was 1- specifically for us and 2 was referring to chicago ATIS. We sent for and received chicago ATIS just prior to descent which gave the barometer setting as 30.27. We did not notice the time on the arrival information was invalid. Shortly after this we received descent instructions including changes to crossing altitudes and speeds which created additional activities while descending. While inputting the arrival restrictions we passed transition level; set 30.27; completed the checklist and then leveled off at what we thought was 13;000 ft. Approach ATC contacted us; asked to confirm our altitude and informed us the correct altimeter was 29.55. We reset our altimeters and climbed back to 13;000 ft. We requested another ATIS which was completely different from the first one and also incorrect. We listened to the audio ATIS which gave the correct info and said at the end that the ATIS was 'unreliable.'the message from dispatch could have been clearer in describing the problem we were about to encounter which I have never in my entire aviation career encountered before (display of completely incorrect ATIS information). For instance: 'attn flight X: chicago digital ATIS is invalid or inaccurate. Here is the current correct weather at kord: do not rely on the ATIS from kord!' plain language would have alerted us to the gravity of the situation. Chicago should also not send known incorrect WX information via digital ATIS. They should shut the system down until it works correctly as expectation bias of always receiving the most up to date ATIS crept into this situation compounding it.

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Original NASA ASRS Text

Title: A crew was on the ORD TRTLL 2 RNAV leveled at 13;000 FT and was queried about their altitude then notified the digital ATIS was wrong and their aircraft was 700 FT low. Digital ATIS nationwide was apparently in error.

Narrative: Had incorrect barometer (30.27 vs 29.55) setting which resulted in leveling off approximately 700 [FT] below assigned altitude of 13;000 FT while descending into Chicago airspace. Received a message from dispatch prior to descend stating 'Attn crews: ATIS is reporting old info. Please check with dispatch for updated WX. The WX request page is still accurate.' We read the message but did not realize this was 1- specifically for us and 2 was referring to Chicago ATIS. We sent for and received Chicago ATIS just prior to descent which gave the barometer setting as 30.27. We did not notice the time on the arrival information was invalid. Shortly after this we received descent instructions including changes to crossing altitudes and speeds which created additional activities while descending. While inputting the arrival restrictions we passed transition level; set 30.27; completed the checklist and then leveled off at what we thought was 13;000 FT. Approach ATC contacted us; asked to confirm our altitude and informed us the correct altimeter was 29.55. We reset our altimeters and climbed back to 13;000 FT. We requested another ATIS which was completely different from the first one and also incorrect. We listened to the audio ATIS which gave the correct info and said at the end that the ATIS was 'unreliable.'The message from dispatch could have been clearer in describing the problem we were about to encounter which I have never in my entire aviation career encountered before (display of completely incorrect ATIS information). For instance: 'Attn flight X: Chicago digital ATIS is invalid or inaccurate. Here is the current correct weather at KORD: Do not rely on the ATIS from KORD!' Plain language would have alerted us to the gravity of the situation. Chicago should also not send known incorrect WX information via Digital ATIS. They should shut the system down until it works correctly as expectation bias of always receiving the most up to date ATIS crept into this situation compounding it.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.