Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Workload; Time Pressure; Human-Machine Interface; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types
Aircraft Equipment Problem Dissipated; Flight Crew Diverted; Flight Crew FLC complied w / Automation / Advisory
Aircraft; Environment - Non Weather Related
Captain (CA) PF; First Officer (FO) PM. At FL370 while in cruise phase just north of ZZZ I noticed my airspeed starting to deteriorate. I glanced over at the FO's instruments and noticed his airspeed increasing. I then disconnected the A/P; A/T and went on Standby Attitude Indicator and began a descent to 16;000 feet; requested priority handling and began running the QRH for IAS Disagree. We also experienced an altimetry anomaly. FO showing high and CA showing low. As we descended my airspeed reached 120 Knots and was below the stick shaker 'hook' on the Speed Tape while the FO's airspeed indicator was showing at or in excess of Maximum. Notified Dispatch; the flight attendants; passengers and ATC. At about FL200 the instruments on our PFDs began to stabilize in the normal range. This particular issue had been written up in the Aircraft Logbook 5 previous times. I asked Operations if they rather have the aircraft in ZZZ1 or ZZZ2. Returned to ZZZ1 as per Operations request. Cruised at 14;000 feet in order to land below MAX Landing Weight. Landed in ZZZ1 at 144;000 pounds with no further incident.Repetitive AML Entry.Keep aircrafts either parked or flying for the duration of this economic downturn; do not rotate aircraft in and out.
[Narrative provided no additional information.]
Air Carrier flight crew reported reoccurring altimeter and airspeed maintenance problems on an aircraft that had been in and out of service several times during the 'economic downturn.'