Treatment of Flights in Stack Hours and Extensions

Flights in Stack Hour

• Stack hours - the hours after the GDP end time

• Flights scheduled to arrive AFTER the GDP end time are EXCLUDED and do NOT get slots

• Example: GDP from 1600-2059– Flight scheduled to arrive at 2059 will be delayed and issued a slot

– Flights scheduled to arrive at 2100 or after will not receive a delay or a slot (not available for substitution)

• Under simplified subs, airlines will be able to voluntarily control excluded flights in the stack hours to re-order flights (Thanks, Roger)

Stack Hour AAR’s Effect on Extensions

• FSM allocates slots in the stack hour based on the stack hour AAR

• If the lower program rate is used (extension expected)– fewer slots will be allocated in each hour

– additional delay may be incurred initially - unrecoverable delay if conditions improve

– controlled flights will receive less additional delay in extensions

• If the higher default AAR is used (extension not expected)– more slots will be allocated

– less delay will be incurred initially

– more delay will be received if there are extensions

• Slots are “reserved” for excluded flights that would be exempt in the case of an extension

SFO 10/30/2000 -6West Example

At 2315, it was decided to run a pure extension from 0200-0359. The stack hours were set to the program rate (30).

Due to the number of cancelled and excluded flights, few slots were left for the non-cancelled controlled flights to fill. The stack extended for five hours.

(Since a pure extension was run, flights were not compressed into cancelled slots that were earlier than 0200.)

AFTER EXTENSION

BEFORE EXTENSION

SFO 10/30/2000 -6West Example

Setting the stack AAR to the default (60) keeps most of the stack in the two hours after the end of the program.

This is a good option when the program is not expected to be extended again. For airports that tend to run programs all day long (LGA), this only postpones the delay flights will eventually obtain.

HIGHER DEFAULT STACK AAR (PURE EXTENSION)

Is There Something Better?

STL 7/28/2000 - ALL Example

At 1654, it was decided to extend the program. With the end time currently at 2159, the spikes after the 2100 hour are normal.

The cancelled flights were moved to the 0300 hour mostly as a result of substitution.

At 1702, the program was extended to 29/0059, pushing a large number of cancelled flights into the 0100 hour and extending the stack for four hours.

BEFORE EXTENSION

AFTER EXTENSION

What Happened?• The cancelled slots showing up in the hour after the end of

the program is not unusual in itself because cancelled flights will be compressed to the end of the program for all non-bridge-only carriers.

• But then the question becomes, “Why weren’t the cancelled slots moved even later since there are so many controlled flights in the 0200 and 0300 hours?”

• Looking at the analysis report from the revision revealed that although all of the cancelled flights were included in RBS, not all of the cancelled flights were included in the compression - Only open slots with slot times before the program end time are eligible for compression in RBS++

How Do We Smooth Out Demand?

• Compression only affects controlled flights so there would still be a spike of light green flights departing without EDCTs in the 0100 hour.

• Extending the program until 0259 to include the cancelled flights and those not previously controlled would smooth out demand.

COMPRESSION WITH END TIME = 9999STL 7/28/2000 - ALL Example

Compression only moves the controlled flights, creating a spike in the 0100 hour.

Extension includes flights not previously controlled as well as the cancelled flights.

EXTENSION WITH 0259 END TIME

What Was Done

STL 7/28/2000 - ALL Example

At 1806, the GDP was extended until 29/0559

Summary

The AAR for the stack hours should be decided based upon the expectations of the program.

•If it appears that an extension will be necessary, keeping the stack AAR lower will help spread out the flights early on.

•If it looks like the program may be cancelled early or not need to be extended, the higher default AAR is acceptable.

Back-up Slides

SFO 10-30-001418 RBS++ 1700 - 2259, 10West, AAR=27, GA Factor=0, Exempt by DEPT. TIME - NOW+(MIN)

45, GS FLTS BY STATUS, Bridge-only Carriers=SWA UAL AAL DAL,Total/Affected Flights=219/114, Total delay=11854, Max delay=175, Avg delay=104, Stack=53Model ADL=1415, Reflect ADL=1423

1650 Arrival delays +151708 Arrival delays -151736 Departure delays +151757 Departure delays -151801 RBS++ 1800 - 0159, 12West, AAR=30, GA Factor=0, Exempt by DEPT. TIME - NOW+(MIN)

45, GS FLTS BY STATUS, Bridge-only Carriers=SWA UAL AAL DAL,Total/Affected Flights=301/139, Total delay=13157, Max delay=263, Avg delay=95, Stack=47Model ADL=1800, Reflect ADL=1804

1805 Arrival delays +151820 Arrival delays +301835 Arrival delays -301841 Arrival delays +301907 Arrival delays -301919 Arrival delays -151925 Arrival delays +151944 Arrival delays +302145 Arrival delays +452156 Arrival delays -452253 Arrival delays +452301 Arrival delays -452302 Arrival delays -302319 RBS++ 0200 - 0359, 6West, AAR=30, GA Factor=0, Exempt by DEPT. TIME - NOW+(MIN) 45,

GS FLTS BY STATUS, Bridge-only Carriers=SWA UAL AAL DAL,Total/Affected Flights=127/57, Total delay=8339, Max delay=262, Avg delay=146, Stack=35Model ADL=2315, Reflect ADL=2323

2341 Arrival delays -150010 6West EDCTs suspended0052 GDP canceled, IMPROVED WEATHER

STL 07-28-001110 Ground Stop 1054 - 1200, All, Exempt by DEPT. STATUS,

Total/Affected Flights=56/47, Total delay before=0, Change=1566, Avg delay before=0.0,Change=33.3Model ADL=1104, Reflect ADL=1113

1154 RBS++ 1149 - 1759, All, AAR=40, GA Factor=0, Exempt by DEPT. STATUS, Bridge-onlyCarriers=AAL NWA,Total/Affected Flights=264/218, Total delay=9234, Max delay=95, Avg delay=42, Stack=29Model ADL=1149, Reflect ADL=1155

1244 RBS++ 1242 - 1759, All, AAR=30/30/40/40/40/40, GA Factor=0, Exempt by DEPT. TIME -NOW+(MIN) 45, GS FLTS BY STATUS, Bridge-only Carriers=AAL NWA,Total/Affected Flights=252/160, Total delay=11648, Max delay=336, Avg delay=73, Stack=52Model ADL=1242, Reflect ADL=1247

1302 Departure delays +151319 Departure delays +301332 RBS++ 1329 - 1959, All, AAR=24/24/24/32/32/32/32, GA Factor=0, Exempt by DEPT. TIME -

NOW+(MIN) 45, GS FLTS BY STATUS, Bridge-only Carriers=AAL NWA,Total/Affected Flights=328/238, Total delay=37200, Max delay=435, Avg delay=156, Stack=128Model ADL=1329, Reflect ADL=1334

1340 Departure delays +451404 Ground Stop 1349 - 1500, All, Exempt by DEPT. STATUS,

Total/Affected Flights=21/18, Total delay before=1296, Change=1023, Avg delay before=72.0,Change=56.8Model ADL=1359, Reflect ADL=1406

1430 Departure delays -451430 Departure delays -301430 Departure delays -151448 RBS++ 1444 - 2159, All, AAR=15/15/15/15/15/32/32/32, GA Factor=0, Exempt by DEPT.

STATUS, Bridge-only Carriers=AAL NWA,Total/Affected Flights=369/306, Total delay=89322, Max delay=380, Avg delay=292, Stack=181Model ADL=1444, Reflect ADL=1449

1502 Departure delays +151535 Departure delays +301618 Compression 1615 - 2159, Bridge-only Carriers=None,

Total/Affected Flights=240/180, Total delay before=63383, Change=-4094, Avg delaybefore=264.1, Change=-17.1Model ADL=1615, Reflect ADL=1620

1625 Departure delays -301643 Departure delays -151636 Departure delays +151641 Departure delays -151659 RBS++ 1654 - 0059, All, AAR=24/24/24/32/32/32/54/54/54, GA Factor=0, Exempt by DEPT.

TIME - NOW+(MIN) 45, GS FLTS BY STATUS, Bridge-only Carriers=AAL NWA,Total/Affected Flights=486/345, Total delay=62914, Max delay=483, Avg delay=182, Stack=97Model ADL=1654, Reflect ADL=1702

1801 RBS++ 1800 - 0559, All, AAR=32/32/32/32/52/52/52/52/52/52/52/52, GA Factor=0, Exempt byDEPT. TIME - NOW+(MIN) 45, GS FLTS BY STATUS, Bridge-only Carriers=AAL NWA,Total/Affected Flights=560/361, Total delay=46503, Max delay=571, Avg delay=129, Stack=0Model ADL=1749, Reflect ADL=1806

1900 RBS++ 1844 - 2159, All, AAR=52, GA Factor=0, Exempt by DEPT. TIME - NOW+(MIN) 45,GS FLTS BY STATUS, Bridge-only Carriers=AAL NWA,Total/Affected Flights=558/330, Total delay=26928, Max delay=529, Avg delay=82, Stack=270Model ADL=1844, Reflect ADL=1903

2005 GDP canceled, UNABLE TO DELIVER AAR