Even in respect of aircraft newly delivered from the factory, a design modification program would be needed to adapt the 777F to this unique mission. This could be done in the 777 production facility, but is more likely to be done in a separate modification line elsewhere. Insulated double-walled pressurized tanks would need to be installed through the existing freighter side door. These tanks should provide safe carriage of the aerosols and maintain it at the desired temperature in flight. The payload weight concentration near the aircraft’s center of gravity will require local strengthening of the main deck and surrounding airframe structure.  An internal plumbing system would need to be developed and installed to enable aerosol loading on the ground and venting at altitude.  Nozzles to vent the aerosols would need to be designed and installed. Local modifications to the aircraft electrical system would be required to provide power to pumps, control valves, and monitoring systems. If required by the FAA, the cargo bay may need to be isolated from the cockpit via a physical pressure bulkhead and positive pressure in the crewstation. This would ensure that an inadvertent escape of the highly toxic aerosols on the ground or in flight would not endanger the flight crew. Modifications to the cockpit instrument panel would allow the crew to manage and control the payload. All of these modifications would need to be engineered, tested, and certified before they could actually be installed in an operational aircraft.
As illustrated in Addendum 1, a reasonable time frame in which to engineer and certify the modification program that would transform the 777F into the 777 Special Tanker might be three years. Thereafter, a fleet of more than 90 777s must be manufactured, and then modified to the Special Tanker configuration. This is far too large a fleet to be sourced second-hand on the open market, so some or all of these would be new deliveries from the factory. Boeing currently produces 36 777s per year41. If the SAI program were to elbow aside the world’s airlines and claim half the production line, it would take another 5 years to build the fleet. 15 aircraft a year is also the rate at which Boeing is delivering new KC-46 tankers to the USAF42, so this is a market-reasonable production rate. Nonetheless, even with an existing aircraft program as our starting point, it would require roughly a decade to stand up the aeronautical infrastructure required to be capable of responding to tipping points in the cryosphere.
5. Ground infrastructure
A decade may prove short in comparison with the span required for the corresponding ground infrastructure. We envision a minimum of four air bases as being required for the polar SAI program – two in the north and two in the south. From a robustness/resilience/reliability standpoint, operating from a single base in each hemisphere would be unreasonably risky. As previously noted, there are several options from which to choose for bases near 60ºN, but for the purpose of this analysis, we focus on the two busiest among them, Anchorage (ANC) and Stockholm (ARN). Each hosts roughly 100,000 aircraft landings per year43,44. While the SAI program would be merely seasonal, during the four month deployment window, daily operations would roughly double at both airports. This would require a rough doubling of capacity of nearly everything at the airport – hotels, fuel storage, maintenance hangars, kitchens, roadways, automobile parking garages, medical facilities, warehouses, etc.
The most acute shortage noted in dialogue and correspondence with the operators of both airports is hard stand aircraft parking spots, so a substantial apron expansion would be required. This would be relatively straightforward for ARN, which owns ample adjacent land, but not so for ANC, which is surrounded by urban development and the Cook Inlet. Nonetheless, with further landfill into the Inlet, such an apron expansion with related hydrant fueling capacity and taxiway infrastructure could occur.  Other identified needs would include 777 maintenance hangar, storage and servicing facilities for additional airfield maintenance and ground service equipment, additional de-icing capacity, crew quarters, and several supplemental storage tanks for fuel and separately for sulfur. 
However, the most substantial further infrastructure requirement would be an additional runway, which would almost certainly be required to accommodate not only an SAI program but projected continued growth in normal passenger and freight operations.  A new 10,000 foot north/south runway and adjacent taxiways at ANC would require a substantial landfill protrusion into Cook Inlet, where a threatened local population of Beluga whales are the object of great local affection45.  Citizen outcry and lawsuits should therefore be expected.  A new runway requirement would boost the total project budget into the low billions of dollars (see Table 5) and define a project span to 12 – 15 years (see Table 6), with the majority of that pertaining to planning, permitting, and approvals46-50. The construction itself could be done in perhaps five years.
Alternatively, building a new airport on a green field site near but not protruding into Cook Inlet would appear to add minimally to the budget and not at all to the span. Choosing a site that is not hemmed in by city and sea would eliminate the landfill requirement and substantially reduce the likely environmental and citizen outcry. The operators at ANC estimate that a brand new airport dedicated to the SAI operation could be built across the inlet on Point Mackenzie for $3 billion.
Given their greater control of adjacent property, ARN might confront fewer land constraints in building out airport capacity. Nonetheless, their estimate for the span to add a runway is 15 – 20 years. Construction itself would require no more than three years, so the vast majority of that span is consumed by planning and approvals. Nonetheless, were a new runway needed by 2040, the airport would need already to be in motion, which it is not.
A novel trans-national financing arrangement may be required to fund any airport build-out for emergency response SAI capability since the timing and likelihood of its use would be highly uncertain. One can imagine the voters of both Alaska and Sweden declining to fund such a project with immense global but limited local benefit. Nonetheless, with sufficient global will, there would undoubtedly be a way to overcome the local politics – there is ample precedent for doubling capacities at major airports.
The same must be true for the southern airports, but problems there are far more acute. Although we might seek a latitudinally symmetrical southern base at or near 60ºS, there is no proximate land mass to accommodate one. The southernmost tips of Africa, Tasmania, and the main islands of New Zealand lie at southern latitudes of 34.5, 43.4, and 47.2 degrees respectively. Stanley, the capital of the Falkland Islands, sits at 51.4°S. South Georgia is farther south at 54.2°S, but hosts only a tiny non-permanent population and no airport. No other islands deeper into the Southern Ocean offer sensible options. The closest landmass to our target latitude lies across the Southern Ocean in the South Shetland Islands at the tip of the Antarctic Peninsula, but this is utterly inhospitable territory lying too far south at 62.1ºS. Hosting the northernmost airport in Antarctica, it has merely a gravel runway a bit longer than 4200 feet.
Re-crossing the Southern Ocean, the tip of Cape Horn is at 56.0°S on an uninhabited island whose notoriously foul weather at the juncture of the world’s two largest oceans has bedeviled sea operations for centuries and would create challenging conditions for air operations as well. The most southerly permanently settled place in the world is Puerto Williams, Chile at 54.9°S on the southern side of the Beagle Channel in Tierra del Fuego. With a population of merely ~2500, its small airport has a single 4700 foot runway that handles roughly 1000 landings per year. In contrast, each airport in the SAI program would call for more than 250 per day on runways twice as long. Moving northward in search of more viable options, next up are Ushuaia, Argentina (54.5ºS) on the opposite (northern) side of the Beagle Channel, and Punta Arenas, Chile (53.0ºS) on the Strait of Magellan. Each has a runway longer than 9000 feet that could accommodate a 777. However, the SAI program would increase daily operations by roughly 20X at Punta Arenas and 30X at Ushuaia.