Date: 202108
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb; Cruise; Descent
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Altimeter
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Distraction; Other / Unknown; Situational Awareness; Troubleshooting; Workload
Second reporter function: Captain
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Passenger Misconduct; Ground Event / Encounter Fuel Issue
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: While climbing out of ZZZ1 enroute to ZZZ I noticed that in RVSM we were close to having a 200 ft. discrepancy between mine and the FO's (First Officer) altimeter.  We didn't go beyond 200 ft. difference and never got an ALT miscompare message.At cruise (FL350) the difference was roughly 130 ft.During descent in to ZZZ; I don't know when exactly it showed up; but I noticed at roughly FL330 during the descent we had a ALT message flashing on my altimeter.  I thought maybe the BARO knob on my side or the FO side got bumped.  I checked and saw that all three altimeters were showing STD.  Then the message went away only to show up 100-200 ft. later.  I looked at the altitudes and saw that we were either 200 or greater but not more than 220 ft. off. But then the next 100-200 ft. we were 200 ft. or less on the miscompare and the ALT message went away only for in the next 100-200 ft. for the ALT message to return and the discrepancy being 200 ft. or greater.It back and forth intermittently until roughly FL290; possibly lower; I do not recall when exactly the issue stopped.I sent an ACARS message to Dispatch to inform them and so that they could inform maintenance so that the issue could start getting worked on when we got to the gate.I also informed ZZZ Operations on the in range call what was going on and that we would need maintenance.I was looking through the QRH to see if there was a checklist for it just in case even though I was pretty sure there wasn't one.This being the first time that this has occurred to me; I unfortunately did not think to reference the standby altimeter to try to help isolate where the fault may lie; as the issue went away while I was diligently looking for a checklist and the issue was intermittent.  Also because it was intermittent and went away on its own I also did not think to inform ATC since we were already in the process of exiting RVSM.No other messages on any display unit; including the EICAS; showed while this was happening nor throughout the remainder of the flight.We landed in ZZZ without incident.I should have known that there wasn't a checklist for this issue and I need to read back up on alt miscompare procedures and how it affects RVSM and what to do.  I should have informed ATC and I should have referenced the standby altimeter to help isolate the problem.  Otherwise I think we did everything else correctly.After working with Maintenance in ZZZ it turns out the number 4 probe had failed even though we didn't get any messages other than the ALT message on the altimeters.  Maintenance said that there when they initially went through their task that there wasn't any active or logged faults with the system and that they had to do another task to isolate where to problem was; in this case the faulty probe.


Second narrative: In ZZZ; during descent we had an ALT disagree message during descent.Upon arrival into ZZZ we had everyone deplane; had maintenance come on and do some checks.They were able to isolate the issue and ascertained it was going to be a lengthy delay.We got word that our new departure time was going to be XE:00 so we got a day room.We got back to the airport at XD:15 for the re-report time.Upon arriving at the aircraft I was informed that there was still work to do but that they just needed to tape a cover back onto the plane for one of the pitot tubes.After that they still needed to do some testing and that it would be about 30 more minutes.So; we went to the crew room to wait for the work to be done.I went back out several times to get updates and each time the return to service kept getting pushed back.Finally; once it became a return to service time of XG:00 I realized that we were going to be within an hour of our FDP (Flight Duty Period) time out in ZZZ1.So; I called scheduling and got a wheels up time of XG:55 before the pilots timed out and due to contractual issues that the main cabin door needed to be closed at XG:34. I was told that Maintenance would call ZZZ Operations who would then call me in the crew room when Maintenance was done in the flight deck and that we could go to the plane; preflight; board; and wait for the maintenance log to come back so we could hopefully get out in time.The call did not come in until roughly XG:10.We went out to the aircraft; I told the flight to not rush the preflight. I told them to take their time; not to slow down so that we didn't hit our times; but so that something wouldn't be missed; prevent mistakes; keep us legal and not on the wrong side of SOPs and Regs.We were able to accomplish our preflight in a timely matter; board in a timely matter; and we were able to get the MCD closed at XG:32. The AML (Aircraft Maintenance Logbook) hadn't returned yet so I figured let's get the door closed so that we hit the Flight Attendant contract time and that hopefully the AML would arrive soon and could be handed to us through the flight deck window.I called Dispatch to make sure we were on the correct revision since we had a hard time getting our IFR clearance. I verified all the fuel and time values along with the correct revision. A few minutes after that a Ramp crew member came to the flight deck informing us that the fuel truck had arrived. There was apparently some confusion about fuel. I initially dismissed the fuel truck only to decide that I should make sure that wasn't any last second changes. So; I called Dispatch to re-verify our fuel numbers. There wasn't any changes and I moved on to the next step.Some time after this the AML arrived around XE:40-XE:45.After the cabin secured and we started our air start checklists due to the APU being INOP.At this point I knew that our timeline most likely wouldn't work but that it would close and that we needed to give our best effort.Right as we got to the part in the checklist to apply air to the aircraft for the air start; the FAs (Flight Attendants) called and informed us that a passenger had gotten up to use the lavatory. I told them to let me know when they had returned and were seated.I told the ground crew to apply air but that we were going to wait for the passenger to come out of the lavatory since the cabin was no longer secured. I do not know if this was the right call but I thought that it was the best call in regards to safety.After a minute or two we got a call from the FAs that there was a possible passenger removal situation going on. I asked what was going on and they informed me that the passenger was being non-compliant with the face mask and was being non-cooperative and nasty in the process.Knowing that we as a whole crew were feeling stressed; tired; and unhappy about all the delays I made sure to ask had we been on time; no maintenance; still XA:30; would this situation rise to the passenger beingremoved. They talked about for a few seconds and agreed that it wasn't. I then instructed them that since he was still being non-compliant; go back one more time and see if we can get him compliant and in line or that we would then look into removal and top report back.After a minute or two I was called back and the FAs informed that the passenger was apologetic and now being compliant and we were good to go.At this point; with the cabin re-secured; I turned back to do the air start. I glanced at the clock to check our time and it was XG:51. At this point I knew that there was no possible way to get the air start; taxi; second engine start; and wheels up at XG:55.I conferred with the FO (First Officer) if he was in agreement and if he was willing to do an extension. He gave valid reason for not doing an extension and agreed with me that there was no possible way that we could get wheels up by XG:55. The reason I asked him was just to get a second opinion and he reaffirmed everything that was already thinking. I had already decided once I saw it was XG:51 that we were done; that there was no point in starting the engines; wasting fuel; taxiing out and turning back. The most efficient and economical path was to admit defeat on there being no possible way to make it off by XG:55 for FDP limit reasons and throw in the towel.We had been fighting a losing battle; we did everything we could to safely get the plane going in time and we just had too many issues pop to delay us going out.I then informed the ramp that we had timed out and to pull the ramp back to the plane and that I would inform the Flight Attendants to do arrival procedures and that we were going to deplane.The FO and did after landing and parking flows and checklists.I then exited the flight deck to tell Flight Attendant A that we were done and to do arrival procedures and that I would inform the passengers.I wanted to be out in the cabin for the announcement to not only own the decision but to not leave our Flight Attendants hanging to deal with potentially irate passengers.I made the PA informing them what was going one; the regulations on duty limits; that we tried our best but unfortunately had timed out and that we need to deplane; that they would be taken care of inside the terminal and apologized profusely for the situation.The passengers got off; mostly understanding; some were understandably irritated; but left without incident.I called crew scheduling to let them know and it sounded like word had gotten around already.We waited with the plane until a hotel was assigned. We then shut down the aircraft; secured it; turned it over to the ramp crew; and left the airport.It was a comedy of setbacks. It was just one thing after another. If it wasn't for the passenger; or the maintenance; or the air start due to the APU being broken; take any one or two items out of the equation and we most likely would have made it. It was a losing battle from the get go; we just didn't know it until the time came were there was no possible way to get out in time.I believe we did everything safely; timely; accurately; with safety and service in mind. At no time did myself; the FO; or FAs intentionally slow down the operation for the goal of timing out. The times we slowdown was to make sure things were done safely and correctly; to catch our breaths; and move on the next step to be completed; all with safety in mind.I do not know what else we could have done. We were ready and on time until the passenger; air start; AML delay; fuel confusion came about. It just wasn't our day.That being said; in order to help speed up AML paperwork we should seriously look into getting electronic AMLs and maintenance. This has a huge potential to cut down the time it takes to get paperwork done. Plus; since we would have access to the AML on our iPads and that the AML lives in the cloud that anyone in the operation can access; we wouldn't have to wait for the AML to come back tothe aircraft. Just like in [program] we would get an alert that the AML is finished; review the changes; sign off on the review; and be on our way in a significantly shorter time.In addition to that; ZZZ is not only a base but also a place where maintenance takes place. There shouldn't be an excuse to not have parts and/or the tools necessary to get jobs done. We shouldn't be having to rely on parts and tools being flown in and we definitely shouldn't be relying on borrowing tools from [other airline] like our maintenance had to do today. I understand that it would be expensive to do all of that but is it more expensive than what we just paid for crew to stay in ZZZ in a more expensive hotel; giving 500-dollar voucher to the passenger in addition to getting them hotel rooms and food vouchers? More expensive than the domino effect that just occurred down the line. Vouchers and hotels were given to those passengers in ZZZ1 no doubt. It's more expensive to not give our Mechanics the resources to do their jobs in a timely fashion than it is to try to save money on parts and tools. Also; across all [aircraft type]; things are failing at; to me; an alarming rate. Be it in the cabin or on the flight deck; these planes are not that old and should not be having things break this much; this fast. We need to stop kicking the can down the road and actually fix things rather than defer and hope for the best. Also; we need to figure out why things are breaking so much so often so soon. This is getting embarrassing and the 3rd major delay; break; cancellation in the past week for me and in talking with other crews and ramp crews; I'm not the only one experiencing these issues. We clearly have systemic issue that we are either unable or unwilling to address and sooner than later it is going to bite us real hard and cause a serious incident or accident.


Synopsis: Air carrier Captain reported a delay followed by a cancelled flight due to a discrepancy between the Captain's and First Officer's altimeters on a previous flight which led to maintenance action.